CVE-2026-113499 in LiteSpeed Cache Plugin
Summary
by MITRE • 10/23/2026
The LiteSpeed Cache WordPress plugin before 7.9.2 does not restrict one of its HTML rewriting routines to stylesheet content, so it removes a quote that terminates an attribute in the rendered page, and combined with unescaped comment author output this allows unauthenticated users whose comment is published to inject attributes that execute JavaScript in the browser of any visitor, including a logged-in administrator, who views front-end pages while the affected option is enabled.
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Analysis
by VulDB Data Team • 10/23/2026
The vulnerability identified in LiteSpeed Cache versions prior to 7.9.2 represents a critical cross-site scripting flaw rooted in improper input validation and output encoding within the plugin's HTML rewriting engine. The core technical defect lies in the failure of one specific routine, designed to optimize or rewrite HTML content for performance improvements, to strictly confine its operations to stylesheet contexts. Instead of limiting processing rules exclusively to CSS data structures, this routine inadvertently processes broader segments of the rendered page markup. This over-eager parsing logic interacts destructively with user-generated content when certain optimization features are active on a WordPress site.
The mechanism of exploitation relies on a specific sequence of events involving comment author output and attribute termination. When an unauthenticated user publishes a comment, their input is stored in the database without sufficient sanitization for this particular context. Upon page rendering, if the vulnerable HTML rewriting routine is enabled, it attempts to process the content. Due to the flaw described, the routine strips or removes a closing quote character from an existing attribute within the rendered HTML structure. This removal effectively breaks the syntax of that specific HTML tag, leaving an open attribute value.
This broken state creates a direct injection vector for malicious JavaScript code. Because the comment author's output is not properly escaped in this context, any script tags or event handlers embedded by the attacker are interpreted as part of the now-open attribute value rather than being treated as literal text data. Consequently, when another user visits the affected page, their browser parses the malformed HTML and executes the injected JavaScript payload within the security context of the vulnerable website. This execution occurs client-side in the victim's browser without requiring any server-side processing for the script itself once it is stored.
The operational impact of this vulnerability is severe due to its unauthenticated nature and broad scope. Any visitor viewing a page with published comments containing malicious payloads can trigger the attack, including site administrators who are logged into WordPress. If an administrator views such a compromised page, their active session cookies and authentication tokens become accessible to the injected script. This allows attackers to perform actions on behalf of the administrator, potentially leading to full website compromise, defacement, data exfiltration, or further propagation of malware through administrative functions that rely on browser-based interactions.
From an industry standard perspective, this vulnerability aligns with CWE-79, which classifies improper neutralization of input during web page generation known as cross-site scripting. The specific technique of breaking out of HTML attributes to inject scripts is a classic manifestation of stored XSS where the payload persists in the database and executes upon subsequent visits. In terms of tactical mapping within the MITRE ATT&CK framework for enterprise security, this behavior corresponds to T1059 Command and Scripting Interpreter via browser-based execution, specifically leveraging client-side scripting languages like JavaScript to achieve unauthorized actions or data theft without direct server exploitation.
Mitigation strategies must prioritize immediate version updates as the primary defense vector. Administrators running LiteSpeed Cache should upgrade to version 7.9.2 or later where this parsing logic has been corrected to strictly isolate stylesheet processing from general HTML content manipulation. Until an update is applied, site administrators can mitigate risk by disabling the specific HTML rewriting feature that triggers the vulnerability if it is not essential for their performance optimization needs. Additionally, implementing a Web Application Firewall with robust cross-site scripting detection rules may help block malicious payloads before they are stored or rendered, although this serves as a compensating control rather than a fix for the underlying code defect. Regular auditing of plugin configurations and keeping all WordPress components updated remains critical to preventing such exploitation chains in dynamic web environments.