CVE-2026-119070 in Optimole Plugin
Summary
by MITRE • 11/07/2026
The Optimole – Optimize Images | Convert WebP & AVIF | CDN & Lazy Load | Image Optimization plugin for WordPress is vulnerable to Stored Cross-Site Scripting via the 'comment' parameter in all versions up to, and including, 4.2.17 due to insufficient input sanitization and output escaping. This makes it possible for unauthenticated attackers to inject arbitrary web scripts in pages that will execute whenever a user accesses an injected page. The exploit requires the plugin to be in its normal connected state (cdn_key and cdn_secret configured) with the image replacer enabled, which is the default post-setup configuration; the stored payload bypasses all WordPress comment sanitization filters because it contains no HTML metacharacters at storage time — the characters are produced only by Optimole's own decoder at render time.
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Analysis
by VulDB Data Team • 11/07/2026
The vulnerability identified in the Optimole plugin for WordPress, specifically affecting versions up to and including 4.2.17, represents a critical Stored Cross-Site Scripting (XSS) flaw rooted in insufficient input sanitization and output escaping mechanisms. This security defect allows unauthenticated attackers to inject arbitrary web scripts into pages served by vulnerable installations. The operational impact is severe because the injected payloads execute automatically whenever any user accesses an affected page that contains the malicious content, potentially leading to session hijacking, defacement, or further malware distribution depending on the context of the compromised site and the privileges of the viewing users.
The technical mechanism behind this vulnerability relies on a sophisticated bypass technique that exploits the specific architecture of how Optimole processes image data. The attack vector targets the comment parameter associated with images processed by the plugin. Crucially, the stored payload is designed to contain no HTML metacharacters at the time of storage. This deliberate obfuscation allows the malicious input to pass through standard WordPress comment sanitization filters and database validation routines without triggering alerts or being stripped out during the initial write operation. The vulnerability manifests only when the content is rendered, as Optimole's own decoder reconstructs the characters that form the executable script at render time rather than storing them in their final harmful form.
For this exploit to be successful, specific environmental conditions must be met within the target WordPress installation. The plugin must be in its normal connected state, meaning both the cdn_key and cdn_secret configuration parameters are correctly set up. Additionally, the image replacer feature must be enabled, which is part of the default post-setup configuration for most users. This combination ensures that images processed through Optimole's CDN infrastructure will trigger the decoding process where the hidden malicious characters are reconstructed, thereby executing the injected script in the victim's browser context without any prior authentication or interaction from an attacker other than triggering the initial storage via a comment field.
From a classification perspective, this vulnerability aligns with CWE-79, which describes Improper Neutralization of Input During Web Page Generation commonly known as Cross-site Scripting. The specific nature of storing malicious content that executes later classifies it under Stored XSS rather than reflected or DOM-based variants. In terms of the MITRE ATT&CK framework, this behavior corresponds to techniques involving input validation bypasses and client-side code injection, specifically mapping to tactics related to Initial Access via phishing-like vectors if social engineering is used to trigger comment submission, followed by Execution through browser script execution. The use of a decoder-based obfuscation technique also highlights the importance of considering how third-party libraries handle data transformation when assessing security boundaries.
Mitigation strategies for this vulnerability primarily involve immediate remediation at the application level. Administrators running vulnerable versions must upgrade the Optimole plugin to version 4.2.18 or later, where these sanitization and escaping issues have been addressed by the developers. Until an update is applied, site administrators should consider disabling the image replacer feature if it is not strictly necessary for their workflow, thereby preventing the rendering path that triggers the vulnerability. Additionally, implementing a Web Application Firewall with rules capable of detecting anomalous patterns in comment submissions or output encoding anomalies can provide a layer of defense against exploitation attempts. Regular auditing of plugin configurations and ensuring that all third-party extensions are kept up to date remains essential for maintaining the integrity of WordPress environments susceptible to such complex injection attacks.