Wpmu Dev · Wpmu Dev Dashboard · CVE-2026-76581
**Name of the Vulnerable Software and Affected Versions**
WPMU DEV Dashboard versions prior to 5.0.2
**Description**
An authentication bypass exists in the Hub SSO flow, potentially affecting approximately 350,000 WordPress sites. The issue stems from HMAC canonicalization confusion—a flaw where data is interpreted differently during signing and verification—between two unauthenticated AJAX actions: `wdpsso step1` and `wdpsso step2`. In `wdpsso step1`, the system signs an unseparated concatenation of the `token`, `state`, `redirect`, and `domain` variables. However, `wdpsso step2` verifies a concatenation that omits the `domain` field. An attacker can use `wdpsso step1` as a signing oracle by requesting a signature with an empty `redirect` field and then replaying that signature to `wdpsso step2` by moving the `domain` value into the `redirect` field. Because the resulting byte strings are identical, the verification passes, allowing an unauthenticated attacker to obtain an authenticated administrator session and potentially achieve full site takeover or remote code execution if the plugin or theme editor is accessible.
**Recommendations**
Update to version 5.0.2.
As a temporary mitigation, disable Hub SSO.