WordPress Time Capsule Plugin 1.21.16 Authentication Bypass

WordPress Time Capsule Plugin 1.21.16 contains an authentication bypass vulnerability that allows unauthenticated attackers to gain administrative access by sending a crafted POST request with the IWP_JSON_PREFIX header. Attackers can exploit this flaw to obtain valid administrator session cookies and access the WordPress dashboard without providing credentials.

The Time Capsule plugin before 1.21.16 for WordPress has an authentication bypass. Any request containing IWP_JSON_PREFIX causes the client to be logged in as the first account on the list of administrator accounts.