vBulletin 5.0.0 through 5.7.5 and 6.0.0 through 6.0.3 allows unauthenticated users to invoke protected API controllers' methods when running on PHP 8.1 or later, as demonstrated by the /api.php?method=protectedMethod pattern, as exploited in the wild in May 2025.
https://kevintel.com/CVE-2025-48827
https://karmainsecurity.com/dont-call-that-protected-method-vbulletin-rce