OpenBao is an open source identity-based secrets management system. Prior to version 2.5.2, OpenBao installations that have an OIDC/JWT authentication method enabled and a role with callback_mode=direct configured are vulnerable to XSS via the error_description parameter on the page for a failed authentication. This allows an attacker access to the token used in the Web UI by a victim. The error_description parameter has been replaced with a static error message in v2.5.2. The vulnerability can be mitigated by removing any roles with callback_mode set to direct.