CVE-2026-4080: Easy Cart WordPress Plugin XSS Vulnerability

CVE-2026-4080 Overview

CVE-2026-4080 is a stored Cross-Site Scripting (XSS) vulnerability [CWE-79] in the Easy Cart plugin for WordPress, affecting all versions up to and including 1.8. The flaw exists in the ectp_add_to_cart() function, which processes shortcode attributes used in the add_to_cart shortcode. The plugin sanitizes attribute values with sanitize_text_field() but fails to escape double quote characters before placing them inside double-quoted HTML attributes. Authenticated users with Contributor-level access or higher can break out of the attribute context and inject arbitrary JavaScript. Injected scripts execute in the browser of any user who views the affected page.

Critical Impact

Authenticated contributors can inject persistent JavaScript into WordPress pages, enabling session theft, administrator account takeover, and arbitrary actions in the context of any visiting user.

Affected Products

• WordPress Easy Cart plugin versions up to and including 1.8
• WordPress sites that allow Contributor-level or higher registration
• Any WordPress installation using the vulnerable add_to_cart shortcode

Discovery Timeline

• 2026-06-02 - CVE-2026-4080 published to NVD
• 2026-06-02 - Last updated in NVD database

Technical Details for CVE-2026-4080

Vulnerability Analysis

The vulnerability resides in the Easy Cart plugin's ectp_add_to_cart() function, which renders the add_to_cart shortcode. The function accepts the attributes itemid, product_name, product_desc, product_qty, and price from user-controlled shortcode input. Each value passes through sanitize_text_field() before being embedded into HTML output inside double-quoted attributes.

sanitize_text_field() removes HTML tags, line breaks, and extra whitespace, but it does not encode quote characters. An attacker supplying a double quote within a shortcode attribute closes the surrounding HTML attribute prematurely. The remaining attacker-controlled bytes are then parsed by the browser as additional attributes, including event handlers such as onmouseover or onfocus. This produces stored XSS persisted within post or page content.

Root Cause

The root cause is the use of sanitize_text_field() as the sole defense for output rendered inside an HTML attribute. The correct WordPress API for this context is esc_attr(), which encodes ", ', <, >, and &. The mismatch between sanitization intent and output context allows attribute-boundary breakout.

Attack Vector

An authenticated user at Contributor level or above creates or edits a post containing the add_to_cart shortcode with a malicious attribute value containing an embedded double quote followed by an event handler. The injected payload is stored in the WordPress database. When any visitor, including administrators, loads the rendered page, the browser executes the attacker's JavaScript under the site's origin. The scope-changed nature of the impact reflects the cross-origin trust violation against viewing users.

No verified proof-of-concept code is publicly available. See the Wordfence Vulnerability Report and the Easy Cart plugin source at line 263 for the vulnerable code paths.

Detection Methods for CVE-2026-4080

Indicators of Compromise

• Post or page content containing add_to_cart shortcode attributes with embedded double quote characters followed by on*= event handler patterns
• Unexpected <script> tags, javascript: URIs, or inline event handlers in rendered Easy Cart product elements
• New or modified posts authored by Contributor accounts that include shortcode payloads referencing external script sources
• Browser console errors or outbound requests to attacker-controlled domains when viewing pages with Easy Cart shortcodes

Detection Strategies

• Query the wp_posts table for post_content matching the regular expression add_to_cart.*"\s*on[a-z]+= to surface injected attribute breakouts
• Review audit logs for Contributor or Author accounts editing pages that use the add_to_cart shortcode
• Inspect rendered HTML on pages using Easy Cart for anomalous attributes outside the expected itemid, product_name, product_desc, product_qty, and price set

Monitoring Recommendations

• Enable WordPress audit logging for post and page modifications, focusing on lower-privileged roles
• Monitor web server access logs for unusual outbound JavaScript fetches initiated from product pages
• Alert on creation of Contributor-level accounts followed by rapid content publishing using shortcodes
• Deploy a Content Security Policy (CSP) that restricts inline script execution and report violations to a monitored endpoint

How to Mitigate CVE-2026-4080

Immediate Actions Required

• Disable or deactivate the Easy Cart plugin until a patched version is installed
• Audit all posts and pages using the add_to_cart shortcode for malicious attribute values
• Review Contributor, Author, and Editor accounts and remove any unrecognized users
• Rotate WordPress administrator passwords and invalidate active sessions if injection is suspected

Patch Information

At the time of NVD publication on 2026-06-02, no fixed version of the Easy Cart plugin has been listed in the available references. Monitor the WordPress Easy Cart plugin repository and the Wordfence advisory for an updated release. The proper fix replaces sanitize_text_field() with esc_attr() on values rendered inside HTML attributes.

Workarounds

• Restrict shortcode usage by removing the add_to_cart shortcode registration or limiting it to trusted roles using a custom mu-plugin
• Apply a Web Application Firewall (WAF) rule that blocks requests containing double quotes followed by on[a-z]+= patterns inside shortcode attributes
• Temporarily downgrade Contributor and Author accounts or require editorial review of all submitted content before publication
• Enforce a strict Content Security Policy that disallows inline event handlers on the front end