CVE-2025-1703: Ultimate Blocks WordPress Plugin XSS Flaw

CVE-2025-1703 Overview

CVE-2025-1703 is a Stored Cross-Site Scripting (XSS) vulnerability in the Ultimate Blocks plugin for WordPress. The flaw affects all versions up to and including 3.2.7. It stems from insufficient input sanitization and output escaping on the content parameter within the responsive-control extension.

Authenticated users with Contributor-level access or above can inject arbitrary JavaScript that executes when any visitor loads an affected page. The weakness is classified as Improper Neutralization of Input During Web Page Generation [CWE-79].

Critical Impact
Authenticated contributors can persist malicious scripts into published pages, enabling session theft, admin account hijacking, and arbitrary actions in the browser context of site visitors and administrators.

Affected Products

Ultimate Blocks plugin for WordPress — all versions up to and including 3.2.7
WordPress sites that permit Contributor-level accounts and above
Sites using the plugin's responsive-control extension

Discovery Timeline

2025-03-26 - CVE-2025-1703 published to the National Vulnerability Database (NVD)
2026-06-17 - Last updated in NVD database

Technical Details for CVE-2025-1703

Vulnerability Analysis

The vulnerability lives in the responsive-control extension of the Ultimate Blocks plugin, specifically in src/extensions/responsive-control/class-responsive-control.php. User-supplied input passed through the content parameter is written into page output without sufficient sanitization or escaping.

Because the stored content is rendered on front-end pages, injected scripts persist across sessions and execute whenever any user visits an affected page. An attacker with Contributor privileges can embed scripts that run in the browser of logged-in administrators, enabling privilege-elevating actions through the WordPress REST API or admin AJAX endpoints.

Root Cause

The root cause is a missing output escaping routine around the content attribute processed by the responsive-control class. WordPress provides functions such as wp_kses_post(), esc_html(), and esc_attr() for context-aware escaping, but the vulnerable code path did not apply them before emitting attribute values into the DOM. See the WordPress Plugin Code and the patch changeset for the exact code locations.

Attack Vector

Exploitation requires an authenticated session with at least Contributor privileges. The attacker crafts a block containing JavaScript payloads in the content parameter and submits the post for review or publication. When an editor, administrator, or site visitor renders the page, the injected script executes in their browser session under the site's origin.

Typical post-exploitation activity includes exfiltrating session cookies, creating rogue administrator accounts via authenticated REST calls, and modifying site content. Refer to the Wordfence Vulnerability Analysis for additional exploitation context.

Detection Methods for CVE-2025-1703

Indicators of Compromise

Unexpected <script> tags, onerror handlers, or javascript: URIs within post content stored in the wp_posts table.
New administrator accounts created shortly after a Contributor-authored post was previewed or published.
Outbound requests from administrator browsers to unfamiliar domains immediately after loading a page containing an Ultimate Blocks responsive-control block.
Modifications to plugin, theme, or user records that cannot be correlated with a legitimate admin session.

Detection Strategies

Inspect posts authored or edited by Contributor-level users for HTML or JavaScript payloads inside Ultimate Blocks block attributes.
Query the database for content attribute values containing <script, onerror=, onload=, or encoded script equivalents.
Review the WordPress audit log for abnormal account privilege changes following post publishing or preview events.
Enable a Web Application Firewall (WAF) rule set that flags stored XSS patterns in wp-admin/admin-ajax.php and REST API block editor endpoints.

Monitoring Recommendations

Log and alert on all requests to /wp-json/wp/v2/blocks and /wp-json/wp/v2/pages that include script-like content fragments.
Monitor browser Content Security Policy (CSP) violation reports for inline script execution on pages rendered by the plugin.
Track plugin version inventory across the WordPress estate to confirm all installations are at the patched release.
Correlate Contributor account activity with subsequent administrator session anomalies.

How to Mitigate CVE-2025-1703

Immediate Actions Required

Update the Ultimate Blocks plugin to a release greater than 3.2.7 that includes WordPress Changeset #3260377.
Audit all Contributor, Author, and Editor accounts, disabling any that are inactive or unverified.
Review recently published and draft posts for injected script content and purge malicious payloads from the database.
Rotate administrator credentials and invalidate active sessions if indicators of compromise are present.

Patch Information

The maintainers addressed the issue in the Ultimate Blocks repository via changeset 3260377, which adds proper sanitization and escaping around the content parameter in class-responsive-control.php. The fix is distributed through the standard WordPress plugin update channel. See the Ultimate Blocks developer page for release details and the changeset file diff for the applied code changes.

Workarounds

Temporarily deactivate the Ultimate Blocks plugin until the patched version is deployed.
Restrict Contributor-level access by requiring editorial review before any post containing Ultimate Blocks components is published.
Deploy a WAF rule that blocks <script>, event handler attributes, and javascript: URIs in block editor payloads.
Enforce a strict Content Security Policy that disallows inline scripts on front-end pages to limit payload execution.

bash

# Configuration example: update the plugin via WP-CLI
wp plugin update ultimate-blocks
wp plugin get ultimate-blocks --field=version