CVE-2026-6255 Overview
CVE-2026-6255 is a Stored Cross-Site Scripting (XSS) vulnerability in the Simple Owl Shortcodes plugin for WordPress. The flaw exists in all versions up to and including 2.1.1 and resides in the num attribute of the owls_wrapper shortcode. The plugin fails to apply sufficient input sanitization and output escaping on user supplied attributes, which is tracked under [CWE-79].
Authenticated attackers with contributor-level access or above can inject arbitrary web scripts into pages. The injected scripts execute in the browsers of any visitors who view the affected page, including administrators.
Critical Impact
Authenticated contributors can persist arbitrary JavaScript into WordPress content, enabling session theft, administrative action forgery, and further site compromise when victims load the injected page.
Affected Products
- Simple Owl Shortcodes plugin for WordPress, versions through 2.1.1
- WordPress sites permitting contributor-level or higher account registration
- Any WordPress installation rendering the owls_wrapper shortcode
Discovery Timeline
- 2026-05-05 - CVE-2026-6255 published to NVD
- 2026-05-05 - Last updated in NVD database
Technical Details for CVE-2026-6255
Vulnerability Analysis
The vulnerability is a Stored Cross-Site Scripting flaw introduced through unsafe handling of shortcode attributes. WordPress shortcodes accept attributes that authors embed directly in post or page content. The Simple Owl Shortcodes plugin processes the owls_wrapper shortcode through inc/owls_wrapper.php, where the num attribute reaches output rendering without sanitization or escaping.
Because WordPress permits contributors to author posts containing shortcodes, an attacker only needs a low-privilege account to plant the payload. The malicious payload persists in the database as part of post content. Each subsequent page render injects attacker-controlled JavaScript into the response, executing in every viewer's browser session within the site origin.
The attack vector is network-based, requires low privileges, and needs no user interaction beyond viewing the page. The scope is changed because injected script runs in the trust context of the WordPress site, allowing impact on other components such as administrator sessions.
Root Cause
The root cause is missing input sanitization on the num shortcode attribute and missing output escaping when the value is emitted into HTML. Secure shortcode handlers should validate that num is numeric, cast it to an integer, or apply WordPress escaping functions such as esc_attr() or esc_html() before rendering. The vulnerable code in the owls_wrapper.php handler concatenates the attribute into output without these controls.
Attack Vector
An attacker authenticates as a contributor or higher, creates or edits a post, and embeds the owls_wrapper shortcode with a crafted num attribute containing JavaScript. After publishing or previewing, the payload is stored in the post and executes whenever a user, including administrators reviewing the submission, accesses the page. The vulnerability can be reviewed in the WordPress Plugin Code Snippet and the Wordfence Vulnerability Report.
Detection Methods for CVE-2026-6255
Indicators of Compromise
- Posts or pages containing owls_wrapper shortcodes with num attribute values that include <script>, onerror=, onload=, or javascript: substrings.
- Unexpected outbound requests from administrator browsers to attacker-controlled domains shortly after viewing contributor-authored content.
- Newly created administrator accounts or modified user roles following review of contributor submissions.
Detection Strategies
- Query the wp_posts table for post_content matching owls_wrapper combined with HTML or script delimiters in attribute values.
- Inspect rendered HTML of pages using the plugin for inline event handlers or <script> tags that originate inside shortcode output.
- Review web server access logs for contributor accounts saving posts containing encoded payloads such as %3Cscript%3E against admin-ajax.php or post.php.
Monitoring Recommendations
- Alert on edits to published content by contributor or author roles, especially when shortcode attributes contain non-numeric data.
- Monitor browser-side Content Security Policy (CSP) violation reports for inline script execution on pages rendering plugin shortcodes.
- Track creation of low-privilege accounts followed quickly by post submissions that include the owls_wrapper shortcode.
How to Mitigate CVE-2026-6255
Immediate Actions Required
- Update the Simple Owl Shortcodes plugin to a version newer than 2.1.1 once the maintainer publishes a fix, or deactivate and remove the plugin.
- Audit existing posts and pages for malicious owls_wrapper shortcode payloads and sanitize or remove affected content.
- Restrict contributor and author registration on internet-facing WordPress sites until remediation is complete.
Patch Information
At the time of publication, the vulnerability affects all versions through 2.1.1. Site administrators should monitor the WordPress plugin repository and the Wordfence Vulnerability Report for an updated release that adds sanitization to the num attribute in inc/owls_wrapper.php.
Workarounds
- Deactivate the Simple Owl Shortcodes plugin until a patched version is available.
- Apply a web application firewall rule to block requests where shortcode attributes contain HTML tags or JavaScript event handlers.
- Enforce a strict Content Security Policy that disallows inline scripts to limit exploitation impact on rendered pages.
- Limit contributor and author roles to trusted users and require editorial review of all shortcodes before publication.
Disclaimer: This content was generated using AI. While we strive for accuracy, please verify critical information with official sources.
