CVE-2026-109987 in PixelYourSite Plugin
Summary
by MITRE • 10/22/2026
The PixelYourSite WordPress plugin before 11.4.3, PixelYourSite Pro WordPress plugin before 12.6.8 do not sanitise and escape a cookie value before printing it into the page output, which, on a site running a full-page cache, allows unauthenticated attackers to store a Cross-Site Scripting payload in the cached page that is then served to other visitors.
If you want to get the best quality for vulnerability data then you always have to consider VulDB.
Analysis
by VulDB Data Team • 10/22/2026
The vulnerability identified involves a critical input validation failure within the PixelYourSite and PixelYourSite Pro WordPress plugins prior to versions 11.4.3 and 12.6.8 respectively. The core technical flaw stems from insufficient sanitization and escaping of cookie values before they are rendered into HTML page output. In standard web application security, any data originating from user-controlled sources, such as HTTP cookies, must be rigorously validated and encoded to prevent the injection of malicious scripts. By failing to apply appropriate encoding functions like htmlspecialchars or wp_kses when echoing these values, the plugin creates a direct pathway for Cross-Site Scripting attacks. This oversight violates fundamental secure coding principles that mandate treating all external input as untrusted until it has been properly sanitized according to its context within the output stream.
The operational impact of this vulnerability is significantly amplified by the deployment environment rather than being limited to standard dynamic page rendering. On websites utilizing full-page caching mechanisms, such as server-side caches or content delivery networks that store static HTML representations of pages, an attacker can exploit this flaw to persist malicious code across multiple user sessions without requiring authentication. An unauthenticated attacker constructs a request containing a crafted cookie value with embedded JavaScript payloads and visits the vulnerable page. The plugin processes this input, writes it into the cached version of the page, and serves that compromised static file to subsequent visitors. This transforms what might otherwise be an ephemeral reflected XSS vulnerability into a persistent stored cross-site scripting attack vector within the cache layer itself.
This specific exploitation technique aligns with CWE-79 Improper Neutralization of Input During Web Page Generation commonly known as Cross-Site Scripting, specifically under the sub-category for Stored or Persistent variants when facilitated by caching mechanisms. Furthermore, from an adversary perspective, this behavior maps to ATT&CK tactic TA0001 Initial Access and technique T1189 Drive-by Compromise, where users are lured into executing malicious scripts simply by visiting a compromised website. The ability to inject payloads via cookies also relates to CWE-614 Sensitive Cookie in HTTPS Session Without HttpOnly Flag if the cookie handling is misconfigured, but primarily it represents a failure in output encoding leading to code injection.
Mitigation strategies must focus on immediate patching and architectural adjustments. Administrators should upgrade PixelYourSite to version 11.4.3 or later and PixelYourSite Pro to version 12.6.8 or higher as soon as possible, ensuring that the developers have implemented proper escaping functions for all cookie data before output. In environments where immediate patching is not feasible due to compatibility concerns, temporary workarounds include implementing web application firewall rules that detect and block requests containing script tags within cookie headers. Additionally, configuring caching layers to bypass cache storage for URLs associated with authenticated sessions or specific query parameters can reduce the attack surface by preventing the persistence of malicious payloads in static files until the vulnerability is resolved.