The Temporary Login plugin for WordPress is vulnerable to Authentication Bypass in versions up to and including 1.0.0. This is due to improper input validation in the maybe_login_temporary_user() function, which fails to verify that the 'temp-login-token' GET parameter is a scalar string before processing it. When the parameter is supplied as an array, PHP's empty() check is bypassed and sanitize_key() returns an empty string, which is then passed as the meta_value to get_users(). WordPress ignores an empty meta_value and returns all users matching the meta_key '_temporary_login_token', allowing authentication without a valid token. This makes it possible for unauthenticated attackers to authenticate as any active temporary login user by sending a single crafted GET request.
The maybe_login_temporary_user() function does not verify whether the GET parameter 'temp-login-token' is a scalar string before processing it. When the parameter is passed as an array, the PHP empty() check is bypassed, and the sanitize_key() function returns an empty string. The empty string is then passed as meta_value to the get_users() function, which in WordPress ignores the empty meta_value and returns all users matching the '_temporary_login_token' meta key. As a result, the attacker gains authentication without needing to possess a valid token.
An unauthenticated attacker can log in as any active temporary user, gaining access to resources and permissions assigned to that account within the WordPress site.
The Temporary Login plugin should be updated to a version higher than 1.0.0, applying patches available from the vendor according to the references. Until the update is applied, it is recommended to deactivate the plugin or restrict access to the website at the network level.
Temporary Login plugin for WordPress in versions up to and including 1.0.0.
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H