Incorrect Implementation of Authentication Algorithm

Developers often rely on proven authentication algorithms like OAuth, SAML, or bcrypt, but a flawed implementation can render these strong protocols ineffective. Common errors include misusing cryptographic functions, incorrectly validating tokens or signatures, or mishandling session state, which creates hidden gaps in the security logic. These implementation flaws can allow attackers to bypass authentication entirely, gain unauthorized access, or escalate privileges. To prevent this, always use well-vetted libraries where possible, follow official implementation guides meticulously, and supplement with rigorous security testing that goes beyond functional checks to validate the actual security behavior.