Executive brief
TaxHacker is a self-hosted AI accounting application for analyzing receipts and transactions. The application uses a hardcoded default JWT secret ('please-set-your-key-here') when administrators don't explicitly configure one, allowing attackers to forge authentication tokens and gain complete unauthorized access to any user's financial data, transactions, files, and settings.
Technical details
The vulnerability is a hardcoded credential weakness (CWE-798) in the JWT secret handler component. The Zod schema in lib/config.ts defines BETTER_AUTH_SECRET with a weak default value 'please-set-your-key-here' (only 24 characters, below the 16-character minimum) that is used as the JWT signing key when the environment variable is not explicitly set. An unauthenticated remote attacker can forge valid JWT session tokens using the known default secret and HS256 algorithm, then use these tokens to bypass authentication and impersonate any user. The attack requires no user interaction or special privileges; it only requires network access to the application. No patch has been confirmed as available at the time of disclosure.
Affected products
- vas3k TaxHacker up to 0.8.2
Timeline
- 2026-08-23: disclosed: Published on NVD
- 2026-07-07: other: Security issue reported on GitHub (#147)