User Session Synchronizer <= 1.4.0 - Unauthenticated Authentication Bypass to Account Takeover via 'ussync-key', 'ussync-token', and 'ussync-ref' Parameters
The User Session Synchronizer plugin for WordPress is vulnerable to Authentication Bypass leading to Account Takeover in all versions up to, and including, 1.4.0. The synchronize_session() function, hooked on init and therefore executed on every request, performs no nonce, capability, or shared-secret validation against the attacker-supplied ussync-key, ussync-token, and ussync-ref parameters; when ussync-key references an unregistered slot, get_option() returns false for both the secret key and the domain list, causing the AES-256-CBC encryption key to degrade to the fully predictable md5('') and the referer allowlist to collapse to an empty-string match, while the AES IV is unconditionally hard-coded as md5('another-secret'). This makes it possible for unauthenticated attackers to supply a crafted request encrypting any known or guessable user email address in the ussync-ref parameter, causing the handler to call wp_set_auth_cookie() for the matched user and granting full authentication as that user — including administrators — with no prior knowledge of site secrets.
Affected software
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| Platform | Package | Vulnerable versions | Fixed in |
|---|---|---|---|
| WordPress plugin | User Session Synchronizer | <= 1.4.0 | no fix |
References
- CVSS vector
CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H- Weakness (CWE)
CWE-287- Platform
- WordPress
- Package
User Session Synchronizer- Disclosed
- 14.08.2026
- Updated
- 11.10.2026 10:23
Sources and licenses
Wordfence Intelligence - cbc32e6d-47c5-4050-ba77-5a54203fe56a - Wordfence Intelligence
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Copyright 2012-2026 Defiant Inc.
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Vulnerability history: User Session Synchronizer
All published vulnerabilities of this package (WordPress plugin), newest first. Shows whether this is a one-off slip or a package that needs watching.
- Total entries
- 2
- First → latest
- 04.2025 08.2026
- Without a fix
- 2
- Exploited in attacks
- 0
Severity breakdown
- Critical 1
- Medium 1
Disclosures per year
- 2025: 1
- 2026: 1
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User Session Synchronizer <= 1.4.0 - Unauthenticated Authentication Bypass to Account Takeover via 'ussync-key', 'ussync-token', and 'ussync-ref' Parameters this entry
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