Auto Thumbnailer <= 1.0 - Authenticated (Contributor+) Arbitrary File Upload
Strategic Overview
- Status
- Unpatched
- Affected Plugin
- Auto Thumbnailer
- Affected Version
<= 1.0- CVSS
- 8.8High
- Weakness type
- CWE-434 · Unrestricted Upload of File with Dangerous Type
- CVE
CVE-2025-12154
At a glance
CVE-2025-12154 is a high-severity Unrestricted Upload of File with Dangerous Type vulnerability in the Auto Thumbnailer WordPress plugin, affecting versions <= 1.0. It carries a CVSS score of 8.8 (reachable over the network; low attack complexity; high confidentiality, integrity, availability impact). Exploitation requires an authenticated account at Contributor level or above. No fixed release has been reported yet; treat installations running this software as exposed. Disclosed December 2025, reported by kr0d.
Vulnerability Overview
The Auto Thumbnailer plugin for WordPress is vulnerable to arbitrary file uploads due to missing file type validation in the uploadThumb() function in all versions up to, and including, 1.0. This makes it possible for authenticated attackers, with Contributor-level access and above, to upload arbitrary files on the affected site's server which may make remote code execution possible.
Technical Analysis
The vector marks this flaw as remotely reachable over the network, with low attack complexity — no special timing or configuration is needed, and no interaction from a victim user. A successful exploit has high impact on confidentiality, integrity, availability — full site compromise territory.
CWE-434: Unrestricted Upload of File with Dangerous Type
Auto Thumbnailer <= 1.0 carries this weakness at uploadThumb(), and reaching it takes an account at Contributor level or above. An unrestricted file upload lets a caller store a file whose type or destination the application does not properly constrain.
If an uploaded file lands anywhere the server will execute, the flaw becomes remote code execution and the site should be treated as fully compromised. No fixed build of this plugin is recorded for Auto Thumbnailer yet, so installs running <= 1.0 stay exposed until the vendor ships one.
Remediation
No known patch available. Please review the vulnerability's details in depth and employ mitigations based on your organization's risk tolerance. It may be best to uninstall the affected software and find a replacement.
How does WordSec protect against this?
An attacker needs Contributor access first, so the firewall sees the attempt as traffic from a logged-in account: WordSec's web application firewall inspects request payloads before WordPress loads them. Classes like this one can leave something behind, so the staged malware scanner is the second half: it looks for dropped files and modified code rather than for the request that created them. No patched version is recorded yet, which is the case where a filtering layer matters most, because there is nothing to update to.
- Firewall
- Scanner
- Alerts
External References
Vulnerability data © Defiant, Inc., provided under the Wordfence Intelligence T&C