Whitespace Flaw Re-Opens Critical JWT “Algorithm Confusion” Bypass

**Executive Summary:** Security researchers disclosed two critical vulnerabilities in the fast-jwt library that enable JWT authentication bypass (algorithm confusion via a regex that fails on leading whitespace) and token cache collisions when custom cacheKeyBuilders are used; both issues carry a CVSS of 9.1, affect fast-jwt <= 6.1.0, and can be mitigated by explicitly specifying algorithms, trimming keys, and auditing configurations.