Captcha 4.3.6 - 4.4.4 - Plugin Backdoor
Strategic Overview
- Status
- Patched in 4.4.5
- Affected Plugin
- Captcha
- Affected Version
4.3.6 – 4.4.4- CVSS
- 9.6Critical
- Weakness type
- CWE-912 · Hidden Functionality
- CVE
CVE pending
At a glance
This record tracks a critical-severity Hidden Functionality vulnerability in the Captcha WordPress plugin, affecting versions 4.3.6 – 4.4.4. It carries a CVSS score of 9.6 (reachable over the network; low attack complexity; high confidentiality, integrity, availability impact). Exploitation requires no authentication. The issue is fixed in version 4.4.5; sites on affected versions should update now. Disclosed December 2017, reported by Matt Barry.
Vulnerability Overview
The Captcha plugin for WordPress contained a backdoor that injected SEO spam into unsuspecting users WordPress sites in version 4.3.6 to 4.4.4.
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. A successful exploit has high impact on confidentiality, integrity, availability — full site compromise territory.
CWE-912: Hidden Functionality
The product contains functionality that is not documented, not part of the specification, and not accessible through an interface or command sequence that is obvious to the product's users or administrators.
Remediation
Update to version 4.4.5, or a newer patched version
How does WordSec protect against this?
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: Captcha 4.4.5 closes this, and updating the plugin is the step that ends it.
- Scanner
- Alerts
External References
Related records
Other vulnerabilities in Captcha
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