a3 Lazy Load <= 2.7.6 - Authenticated (Contributor+) Stored Cross-Site Scripting via Video Element
Strategic Overview
- Status
- Patched in 2.7.7
- Affected Plugin
- a3 Lazy Load
- Affected Version
<= 2.7.6- CVSS
- 6.4Medium
- Weakness type
- CWE-79 · Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
- CVE
CVE-2026-6427
At a glance
CVE-2026-6427 is a medium-severity Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') vulnerability in the a3 Lazy Load WordPress plugin, affecting versions <= 2.7.6. It carries a CVSS score of 6.4 (reachable over the network; low attack complexity). Exploitation requires an authenticated account at Contributor level or above. The issue is fixed in version 2.7.7; sites on affected versions should update now. Disclosed May 2026, reported by theviper17y.
Vulnerability Overview
The a3 Lazy Load plugin for WordPress is vulnerable to Stored Cross-Site Scripting in all versions up to, and including, 2.7.6 This is due to a regex bug in the _filter_videos() method that breaks HTML attribute quoting when processing crafted <video> elements, combined with unescaped output in the admin/views/form-data.php template. An authenticated attacker with Contributor-level access can insert a crafted <video> tag whose src attribute contains an embedded class=" substring that tricks the plugin's class-replacement regex into consuming an attribute-value closing quote. This shifts the HTML5 parser's quote boundary, promoting attacker-controlled text from inside a quoted attribute value into standalone event-handler attributes (autofocus, onfocus). The injected script executes in the browser of any user (including administrators) who views the post.
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')
a3 Lazy Load <= 2.7.6 carries this weakness at _filter_videos(), and reaching it takes an account at Contributor 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. For a3 Lazy Load the fix is 2.7.7: builds <= 2.7.6 are affected, anything from 2.7.7 onward is not.
Remediation
Update to version 2.7.7, or a newer patched version
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. None of that substitutes for the fix: a3 Lazy Load 2.7.7 closes this, and updating the plugin is the step that ends it.
- Firewall
- Alerts
External References
Related records
Other vulnerabilities in a3 Lazy Load
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