AccessPress Anonymous Post Pro <= 3.1.9 - Unauthenticated Arbitrary File Upload
Strategic Overview
- Status
- Patched in 3.2.0
- Affected Plugin
- accesspress-anonymous-post-pro
- Affected Version
< 3.2.0- CVSS
- 9.8Critical
- Weakness type
- CWE-434 · Unrestricted Upload of File with Dangerous Type
- CVE
CVE-2017-16949
At a glance
CVE-2017-16949 is a critical-severity Unrestricted Upload of File with Dangerous Type vulnerability in the accesspress-anonymous-post-pro WordPress plugin, affecting versions < 3.2.0. It carries a CVSS score of 9.8 (reachable over the network; low attack complexity; high confidentiality, integrity, availability impact). Exploitation requires no authentication. The issue is fixed in version 3.2.0; sites on affected versions should update now. Disclosed December 2017, reported by Colette Chamberland.
Vulnerability Overview
An issue was discovered in the AccessKeys AccessPress Anonymous Post Pro plugin through 3.1.9 for WordPress. Improper input sanitization allows the attacker to override the settings for allowed file extensions and upload file size, related to inc/cores/file-uploader.php and file-uploader/file-uploader-class.php. This allows the attacker to upload anything they want to the server, as demonstrated by an action=ap_file_upload_action&allowedExtensions[]=php request to /wp-admin/admin-ajax.php that results in a .php file upload and resultant PHP code execution.
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 privileges on the target site, 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
Reaching this weakness in accesspress-anonymous-post-pro < 3.2.0 takes no account at all. 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. For accesspress-anonymous-post-pro the fix is 3.2.0: builds < 3.2.0 are affected, anything from 3.2.0 onward is not.
Remediation
Update to version 3.2.0, or a newer patched version
How does WordSec protect against this?
Requests carrying this pattern arrive without a session, so nothing upstream of the firewall gets a chance to reject them: 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. None of that substitutes for the fix: accesspress-anonymous-post-pro 3.2.0 closes this, and updating the plugin is the step that ends it.
- Firewall
- Scanner
- Login Security
External References
Vulnerability data © Defiant, Inc., provided under the Wordfence Intelligence T&C