Light Messages <= 1.0 - Authenticated (Admin+) Cross-Site Scripting
Strategic Overview
- Status
- Unpatched
- Affected Plugin
- Light Messages
- Affected Version
<= 1.0- CVSS
- 6.1Medium
- Weakness type
- CWE-79 · Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
- CVE
CVE-2021-24535
At a glance
CVE-2021-24535 is a medium-severity Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') vulnerability in the Light Messages WordPress plugin, affecting versions <= 1.0. It carries a CVSS score of 6.1 (reachable over the network; low attack complexity). Exploitation requires no authentication. No fixed release has been reported yet; treat installations running this software as exposed. Disclosed July 2021, reported by Vinay Bhuria.
Vulnerability Overview
The Light Messages WordPress plugin through 1.0 is lacking CSRF check when updating it's settings, and is not sanitising its Message Content in them (even with the unfiltered_html disallowed). As a result, an attacker could make a logged in admin update the settings to arbitrary values, and set a Cross-Site Scripting payload in the Message Content. Depending on the options set, the XSS payload can be triggered either in the backend only (in the plugin's settings), or both frontend and backend.
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.
CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
Reaching this weakness in Light Messages <= 1.0 takes an account at Admin level or above. 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. No fixed build of this plugin is recorded for Light Messages 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 Admin 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. No patched version is recorded yet, which is the case where a filtering layer matters most, because there is nothing to update to.
- Firewall
- Alerts
External References
Vulnerability data © Defiant, Inc., provided under the Wordfence Intelligence T&C