The vulnerability stemmed from three key issues: 1) Missing validation of JWT expiration/subject claims in GetTokenClaimsIfValid, 2) Use of a weak static signing key in GetSignedTokenString, and 3) Over-reliance on external token validation in ValidateToken without JWT claim checks. The commits show these were addressed by adding claim validation (ExpiresAt, Subject, SessionId), enforcing secure signing keys, and removing the insufficient ValidateToken method. The CWEs (295/384/613) directly map to these flaws in JWT handling and session management.