This tweet mentions a Web Application Firewall (WAF) bypass technique targeting applications using Spring Boot. The bypass method involves using double slashes '//' and semicolons ';' in the input or request. These characters can be used to confuse or evade the WAF's filtering rules, potentially allowing malicious payloads to get through.

Spring Boot is a popular framework for building Java web applications. Often, security mechanisms such as WAFs are deployed to protect these applications from attacks like SQL Injection (SQLi), Cross-Site Scripting (XSS), Remote Code Execution (RCE), and others.

The bypass leveraging '//' and ';' suggests that the WAF might be parsing or interpreting input incorrectly, allowing crafted inputs to bypass detection. Double slashes can act as a comment or path separator, and semicolons can be used to separate statements or commands, which might mislead the WAF.

For example, an attacker might insert these characters in malicious payloads to trick the WAF into ignoring part of the input or to split commands, thus evading filters designed to block harmful patterns.

If you are running a Spring Boot application behind a WAF, it's crucial to ensure that your WAF rulesets properly handle such characters and do not allow bypass via these techniques. Regularly update your WAF signatures and perform security audits to identify potential weaknesses.

In summary, this bypass technique highlights the need for comprehensive input validation and WAF configurations that consider unusual but valid input characters such as '//' and ';'.