CVE-2026-103070 in Image Optimizer Plugin
Summary
by MITRE • 10/08/2026
Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') vulnerability in ShortPixel ShortPixel Image Optimizer shortpixel-image-optimiser allows Stored XSS.This issue affects ShortPixel Image Optimizer: from n/a through 6.5.6.
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Analysis
by VulDB Data Team • 10/08/2026
The identified security flaw represents a classic instance of Improper Neutralization of Input During Web Page Generation, commonly known as Cross-site Scripting or XSS. Specifically, this vulnerability manifests as a Stored XSS within the ShortPixel Image Optimizer plugin for WordPress. Unlike reflected XSS attacks where malicious scripts are embedded in URLs and executed immediately upon user interaction with a link, stored vulnerabilities persist on the target server. In this context, an attacker can inject malicious JavaScript code into input fields that are subsequently saved to the database without proper sanitization or encoding. When other users, including administrators, view pages containing these optimized images or related metadata, the browser executes the embedded script in their session context. This persistence distinguishes it from transient attacks and significantly increases its potential for widespread impact across a WordPress installation.
The technical root cause lies in the insufficient validation of user-supplied data during the web page generation phase. The plugin fails to adequately neutralize special characters or escape output when rendering content associated with image optimization processes. By allowing raw script tags or event handlers to be stored and later rendered by the browser, the application violates fundamental security principles regarding input handling. This failure enables an attacker who has access to any writable area within the WordPress environment where this plugin operates to inject arbitrary code. The scope of affected versions spans from no specific lower bound through version 6.5.6, indicating that a significant portion of installations using older or current iterations are susceptible unless patched.
The operational impact of such a vulnerability is severe and multifaceted. Once the malicious script is executed in the context of an authenticated user's browser session, it can perform actions on behalf of that user with their privileges. For WordPress administrators, this could mean complete compromise of the website, including defacement, data exfiltration, or installation of further malware such as web shells or backdoors. Even for lower-privilege users like editors or authors, stored XSS can be used to steal session cookies, hijack sessions, or perform unauthorized actions within the admin dashboard. Furthermore, because the payload is stored on the server, it affects every user who views the compromised content, potentially leading to a large-scale compromise if an administrator visits a page containing the malicious script. This aligns with CWE-79, which categorizes improper neutralization of input during web page generation as a critical weakness in application security design and implementation.
From a threat intelligence perspective, this vulnerability maps directly to MITRE ATT&CK techniques related to Client-Side Scripting Injection. Attackers can leverage stored XSS for initial access or privilege escalation if the victim has elevated permissions. The persistence of the payload allows for long-term surveillance or repeated exploitation without needing to re-inject code each time. This makes it particularly dangerous in environments where multiple users interact with content managed by plugins that handle media files, as images are a common vector for embedding malicious metadata or triggering execution through associated UI elements like alt text fields, titles, or description boxes processed by the optimizer.
Mitigation strategies must focus on immediate remediation and defensive coding practices. The primary defense is to upgrade ShortPixel Image Optimizer to a version newer than 6.5.6 where this vulnerability has been addressed by the developers through proper input sanitization and output encoding. Until an update is applied, administrators should consider disabling the plugin if it is not strictly necessary for their workflow. Additionally, implementing Web Application Firewalls can help detect and block attempts to inject script tags into form submissions or API calls associated with image optimization. Security best practices dictate that all user inputs must be validated against a whitelist of expected values where possible, and any data rendered in HTML contexts must be properly encoded using context-aware escaping techniques such as HTML entity encoding for text content and URL encoding for attributes. Regular security audits and penetration testing can further identify similar flaws in other plugins or custom code within the WordPress ecosystem to ensure comprehensive protection against client-side injection attacks.