The tweet suggests a logic bypass for WAF authentication that requires the request to be from localhost. The bypass involves using the value 'localhost' or '' to trick the WAF into authenticating the request as if it is coming from the local machine. This can potentially allow an attacker to bypass the authentication checks and access restricted resources. This type of bypass can impact various WAF vendors and highlights the importance of properly configuring WAF rules to prevent such bypasses.
For more details, check out the original tweet here: