CVE-2026-1854
Stored XSS in WordPress Post Flagger Plugin Allows Script Injection
Publication date: 2026-03-21
Last updated on: 2026-03-21
Assigner: Wordfence
Description
Description
CVSS Scores
EPSS Scores
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Meta Information
Affected Vendors & Products
| Vendor | Product | Version / Range |
|---|---|---|
| wordfence | post_flagger | to 1.1 (inc) |
| post_flagger | post_flagger | to 1.1 (inc) |
Helpful Resources
Exploitability
| CWE ID | Description |
|---|---|
| CWE-79 | The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users. |
Attack-Flow Graph
AI Powered Q&A
Can you explain this vulnerability to me?
CVE-2026-1854 is a Stored Cross-Site Scripting (XSS) vulnerability in the Post Flagger plugin for WordPress, affecting all versions up to and including 1.1. The vulnerability arises because the plugin does not properly sanitize or escape user-supplied attributes in its 'flag' shortcode. This allows authenticated users with contributor-level access or higher to inject arbitrary web scripts into pages. These scripts execute whenever any user accesses the affected page, potentially compromising user data or site integrity.
How can this vulnerability impact me? :
This vulnerability can impact you by allowing authenticated users with contributor-level access or above to inject malicious scripts into your WordPress site pages. These scripts execute in the browsers of users who visit the infected pages, potentially leading to theft of user credentials, session hijacking, defacement, or other malicious actions. Because the attack is stored, the malicious code persists and affects all visitors to the compromised pages.
How does this vulnerability affect compliance with common standards and regulations (like GDPR, HIPAA)?:
I don't know
How can this vulnerability be detected on my network or system? Can you suggest some commands?
[{'type': 'paragraph', 'content': "This vulnerability involves the Post Flagger WordPress plugin versions up to 1.1, which is vulnerable to Stored Cross-Site Scripting via the 'flag' shortcode. Detection involves identifying if the vulnerable plugin is installed and active on your WordPress site."}, {'type': 'paragraph', 'content': "To detect the presence of the vulnerable plugin, you can check the installed plugins directory for 'post-flagger' and verify its version."}, {'type': 'list_item', 'content': 'On the server hosting WordPress, run: ls wp-content/plugins/post-flagger'}, {'type': 'list_item', 'content': "Check the plugin version by inspecting the main plugin file: grep 'Version' wp-content/plugins/post-flagger/post-flagger.php"}, {'type': 'paragraph', 'content': "To detect exploitation attempts or suspicious activity related to this vulnerability, monitor HTTP requests for usage of the 'flag' shortcode or AJAX calls to 'admin-ajax.php' with the action 'flag_post'."}, {'type': 'list_item', 'content': "Use web server logs to search for POST requests to admin-ajax.php with 'action=flag_post': grep 'admin-ajax.php' /var/log/apache2/access.log | grep 'action=flag_post'"}, {'type': 'list_item', 'content': "Look for unusual or suspicious input in the 'flag_action' POST parameter that might indicate attempts to exploit the dynamic function call vulnerability."}] [1, 3]
What immediate steps should I take to mitigate this vulnerability?
[{'type': 'paragraph', 'content': 'Immediate mitigation steps include disabling or removing the vulnerable Post Flagger plugin from your WordPress installation, as it has been removed from official availability pending a security review.'}, {'type': 'paragraph', 'content': 'Restrict access to the WordPress admin area to trusted users only, especially limiting contributor-level access and above, since authenticated users with such access can exploit this vulnerability.'}, {'type': 'paragraph', 'content': "Monitor and block suspicious AJAX requests to 'admin-ajax.php' with the 'flag_post' action, potentially using a web application firewall (WAF) or security plugin to filter malicious input."}, {'type': 'paragraph', 'content': 'Apply principle of least privilege by reviewing user roles and capabilities to minimize the number of users who can execute flagging actions.'}, {'type': 'paragraph', 'content': 'Keep your WordPress core and plugins updated, and watch for any security patches or updates released for the Post Flagger plugin once available.'}] [1, 3]