Discuz! X5.0 releases 20260320 through 20260501 contains an authentication bypass vulnerability that allows unauthenticated remote attackers to gain unauthorized access to database backup and restore functionality by exploiting a shared cryptographic key between UCenter integration and the database backup API exposed by dbbak.php. Attackers can inject a crafted payload through the username parameter during login to abuse the encryption oracle in loggingctl::loggingmore(), obtain a legitimately signed token, and use it to bypass authorization for database export and import operations, with the additional ability to trigger a race condition to impersonate arbitrary users.

Discuz! X5.0 releases 20260320 through 20260610 contains a CAPTCHA bypass vulnerability that allows unauthenticated remote attackers to defeat challenge controls by exploiting limited complexity and predictable character sets in generated CAPTCHA images. Attackers can train a custom optical character recognition model against collected CAPTCHA samples to reliably predict challenge text, bypassing protections on login, registration, and other functionality from automated abuse.

A vulnerability was found in Comsenz Discuz! X5.0-20260801/X5.0-20260820/X5.0-20260910. Affected by this issue is the function modmedalsubmit of the file upload/source/app/admin/child/medals/mod.php of the component Admin Medal Moderation. The manipulation of the argument delete results in sql injection. It is possible to launch the attack remotely. The exploit has been made public and could be used. The vendor was contacted early about this disclosure but did not respond in any way.