The tweet describes a bypass for Cloudflare WAF using an XSS payload. The bypass was achieved by using a variation of the 'onerror' attribute which was able to bypass Cloudflare's heuristics. The payload was then amended to execute an XSS attack. This bypass highlights a potential security vulnerability in Cloudflare WAF's detection mechanisms.
Check out the original tweet here: https://twitter.com/Shad0wH3x/status/1812324200226697467