CVE-2025-5528: Sassy Social Share XSS Vulnerability

CVE-2025-5528 Overview

CVE-2025-5528 is a Reflected Cross-Site Scripting (XSS) vulnerability affecting the Sassy Social Share plugin for WordPress. The flaw exists in all versions up to and including 3.3.75. It stems from insufficient input sanitization and output escaping on the heateor_mastodon_share parameter [CWE-79]. Unauthenticated attackers can inject arbitrary web scripts that execute in a victim's browser after the victim clicks a crafted link. The vulnerability was published to the National Vulnerability Database (NVD) on June 7, 2025.

Critical Impact
Unauthenticated attackers can execute arbitrary JavaScript in a victim's browser session, enabling session hijacking, credential theft, and redirection through a single crafted link.

Affected Products

Heateor Sassy Social Share plugin for WordPress, all versions through 3.3.75
WordPress sites using the affected heateor:sassy_social_share component
Any site exposing the heateor_mastodon_share parameter to unauthenticated users

Discovery Timeline

2025-06-07 - CVE-2025-5528 published to NVD
2026-06-17 - Last updated in NVD database

Technical Details for CVE-2025-5528

Vulnerability Analysis

The Sassy Social Share plugin processes the heateor_mastodon_share request parameter and reflects its value back into rendered HTML output. The plugin does not sanitize the input or escape the output before insertion into the response body. Attackers embed JavaScript payloads inside the parameter value, and the plugin returns them in the page as executable script content. Because delivery requires user interaction, an attacker distributes a malicious URL through phishing, forum posts, or social media. When a target follows the link, the script runs in the context of the vulnerable WordPress site. The scope-changed nature of the flaw allows scripts to affect resources beyond the initial component, including authenticated administrator sessions.

Root Cause

The vulnerability originates in the plugin's public request handler, referenced at public/class-sassy-social-share-public.php line 1481 in the 3.3.75 tag. The code path accepts the heateor_mastodon_share value without applying WordPress escaping functions such as esc_html(), esc_attr(), or sanitize_text_field(). This missing output encoding is the direct cause of the reflected XSS condition.

Attack Vector

Exploitation requires network access and one user interaction. An attacker crafts a URL to a vulnerable WordPress page and appends a malicious payload to the heateor_mastodon_share query parameter. The attacker distributes the URL, and any visitor who clicks it triggers script execution in their browser under the target site's origin.

No verified public exploit code is available. See the WordPress Plugin Code Reference and the Wordfence Vulnerability Report for technical details.

Detection Methods for CVE-2025-5528

Indicators of Compromise

HTTP requests containing the heateor_mastodon_share parameter with values that include <script>, javascript:, or HTML event handler substrings such as onerror= and onload=
Referrer chains showing users arriving at the site from external phishing domains before script execution
Unexpected outbound requests from authenticated administrator browsers to attacker-controlled hosts following a click on an external link

Detection Strategies

Inspect WordPress access logs and Web Application Firewall (WAF) telemetry for encoded payloads targeting heateor_mastodon_share, including URL-encoded and Unicode variants
Deploy signatures matching reflected XSS patterns on any request path served by the Sassy Social Share plugin
Correlate parameter tampering events with subsequent administrator session activity to identify successful exploitation

Monitoring Recommendations

Enable verbose HTTP request logging on WordPress front-end nodes and forward events to a centralized SIEM
Alert on any request to a plugin endpoint containing script tags or JavaScript URI schemes in query parameters
Track version metadata of installed WordPress plugins and flag hosts still running Sassy Social Share 3.3.75 or earlier

How to Mitigate CVE-2025-5528

Immediate Actions Required

Inventory all WordPress sites and identify installations of the Heateor Sassy Social Share plugin
Update the plugin to a version later than 3.3.75 once released by the vendor
Enable a Web Application Firewall rule blocking script tags and JavaScript URI schemes in the heateor_mastodon_share parameter
Restrict administrator access to trusted networks to reduce phishing exposure

Patch Information

At the time of publication, no fixed version is listed in the enriched CVE data. Monitor the Wordfence Vulnerability Report and the plugin's WordPress.org page for a patched release, and apply it as soon as it becomes available.

Workarounds

Deactivate the Sassy Social Share plugin until a patched version is installed
Configure a WAF rule to strip or block the heateor_mastodon_share parameter when it contains HTML control characters
Set a strict Content Security Policy (CSP) header that disallows inline scripts on pages served by the plugin

bash

# Example ModSecurity rule blocking script payloads in the vulnerable parameter
SecRule ARGS:heateor_mastodon_share "@rx (?i)(<script|javascript:|on[a-z]+\s*=)" \
    "id:1005528,phase:2,deny,status:403,log,msg:'CVE-2025-5528 XSS attempt blocked'"