WHMCS Bridge <= 6.1 Subscriber+ Stored Cross-Site Scripting
Strategic Overview
- Status
- Patched in 6.3
- Affected Plugin
- WHMCS Bridge
- Affected Version
<= 6.1- CVSS
- 6.4Medium
- Weakness type
- CWE-79 · Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
- CVE
CVE-2021-4074
At a glance
CVE-2021-4074 is a medium-severity Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') vulnerability in the WHMCS Bridge WordPress plugin, affecting versions <= 6.1. It carries a CVSS score of 6.4 (reachable over the network; low attack complexity). The issue is fixed in version 6.3; sites on affected versions should update now. Disclosed January 2022, reported by Kazuto Kokonoe.
Vulnerability Overview
The WHMCS Bridge WordPress plugin is vulnerable to Stored Cross-Site Scripting via the cc_whmcs_bridge_url parameter found in the ~/whmcs-bridge/bridge_cp.php file which allows attackers to inject arbitrary web scripts, in versions up to and including 6.1. Due to missing authorization checks on the cc_whmcs_bridge_add_admin function, low-level authenticated users such as subscribers can exploit this vulnerability.
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.
CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
Reaching this weakness in WHMCS Bridge <= 6.1 takes a caller who can reach the endpoint. Cross-site scripting happens when input from a request is written into a page without being escaped for the context it lands in, so the browser parses attacker-supplied text as markup or script.
Injected script runs with the privileges of whoever views the affected page, which is how these flaws turn into administrator session theft, silent account creation or persistent backdoors in page content. For WHMCS Bridge the fix is 6.3: builds <= 6.1 are affected, anything from 6.3 onward is not.
Remediation
Update to version 6.3, or a newer patched version
How does WordSec protect against this?
The attempt arrives as an ordinary request to WHMCS Bridge: WordSec's web application firewall inspects request payloads before WordPress loads them. None of that substitutes for the fix: WHMCS Bridge 6.3 closes this, and updating the plugin is the step that ends it.
- Firewall
- Alerts
External References
Related records
Same weakness class
Other vulnerabilities in WHMCS Bridge
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