Microsoft’s SharePoint platform is facing active exploitation following the public release of a proof-of-concept (PoC) for a critical authentication bypass vulnerability tracked as CVE-2026-55040. Patched in July’s Patch Tuesday, the flaw allows unauthenticated actors to impersonate SharePoint users by forging JSON Web Tokens (JWTs). Since the PoC surfaced, security researchers and telemetry providers have observed real-world attempts that underscore the