Postiz Weak Random Number Generator Lets Attackers Predict Credentials

A vulnerability in Postiz is caused by weak random number generation: security-sensitive credentials are created with Math.random() instead of a cryptographically secure source. The same helper is used for:

• OAuth access tokens
• authorization codes
• client secrets
• organization API keys
• PKCE verifiers

These credentials therefore depend entirely on V8’s deterministic xorshift128+ PRNG state. An unauthenticated OAuth dynamic client registration endpoint exposes freshly generated client credentials, giving attackers enough consecutive PRNG output to reconstruct that internal state.

Once recovered, they can deterministically derive past and future values produced by the same generator, potentially compromising credentials belonging to other users and organizations.