The tweet suggests that a SQL injection attempt was blocked by a Web Application Firewall (WAF). It highlights that the WAF may be the reason for the block, not the application's security measures. The tweet metaphorically compares the WAF to a shield that hides the true security status of the application, like a child hiding behind a parent. By bypassing the WAF, the application is exposed, revealing its true vulnerabilities. This emphasizes the importance of proper application security measures in addition to relying on WAF protection. The bypass payload used is described as 'UNIVERSAL' suggesting a generic bypass technique that can potentially work across different WAF vendors.
For more details, check out the original tweet here: https://twitter.com/40sp3l/status/1930745093675454941