Post: x3CTF - blogdog (+ new CSS Injection XS-Leak!) | Jorian Woltjer A "hard web xssbot" challenge about a fun browser quirk with the is= attribute to perform CSS Injection. Bypass the strict CSP with an unintended new technique to XS-Leak a selector's result by detect...

During #x3ctf, I discovered an unintended solution that turned out to be a pretty cool generic technique. It allows you to detect the result of a selector during CSS Injection, bypassing any CSP restricting external requests!
Check out the writeup below:
jorianwoltjer.com/blog/p/ctf/x...