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By Bamdad Shahabi | CAISD — Cyber Intelligence & Digital Forensics
youtube.com/@CAISD_Official
XSS has been in OWASP Top 10 for 20+ years.
Nobody handled it.
What is XSS?
XSS (Cross-Site Scripting) allows attackers
to inject malicious scripts into trusted websites.
The browser executes them because they appear
to come from a legitimate source.
How does XSS steal your session?
A user logs into their bank.
An attacker already stored this as a "comment":
Server stored it. No sanitization. No filtering.
Browser loads page — runs the script.
Session token flies to evil.io.
No password touched. Just trust abused.
The 3 types of XSS
① Stored XSS — payload in database,
hits every user. P1 severity in bug bounty.
② Reflected XSS — bounces from URL,
needs a click. P2 severity.
③ DOM-based XSS — client-side only.
Server never sees it. WAFs are blind to it.
Bug Bounty severity
| Type | Severity |
|---|---|
| Stored XSS authenticated endpoint | P1 |
| Session hijack via document.cookie | P1 |
| Reflected XSS on login page | P2 |
| DOM XSS bypassing WAF | P2 |
How to prevent XSS
✅ Content-Security-Policy:
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