Postiz generates security-sensitive credentials using Math.random() instead of a cryptographically secure source. The same helper is used for OAuth access tokens, authorization codes, client secrets, organization API keys, and PKCE verifiers, meaning these credentials 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.
The anonymous sampling surface, the OAuth dynamic client registration endpoint, is registered in both the default controller set and the MCP_ONLY controller set, so it is reachable in either deployment mode.
No public exploit code is known. The original submission was methodology-only and deliberately omitted a working implementation.
Where the deployment allows it, restricting the public API to known client networks limits who can present a predicted credential. This is a containment measure for the consequence rather than a fix for the predictability.
Operators who connected social accounts while running an affected version should review those connections, since the PKCE verifiers used to establish them were drawn from the same generator.