The tweet describes a scenario where an endpoint allowed PDF uploads without authentication, but other types of uploads were blocked by the WAF (Web Application Firewall). The usual bypass tricks failed to work. More steps were involved in the bypass process. The specific vulnerability type is not mentioned, and the WAF vendor is unknown. It would be beneficial to provide further details about the bypass steps and the WAF behavior in a comprehensive write-up.
Check out the original tweet here: https://twitter.com/VailSec/status/1927418019707334923