CVE-2026-85158 in AVideo
Summary
by MITRE • 09/03/2026
AVideo through commit c91b5975d contains a reflected cross-site scripting vulnerability in videoEmbeded.php that echoes the link parameter inside an HTML comment with zero escaping. Attackers can close the comment with --> and inject arbitrary JavaScript that executes when victims visit the crafted embed URL.
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Analysis
by VulDB Data Team • 09/03/2026
The identified vulnerability represents a classic instance of Reflected Cross-Site Scripting, formally categorized under CWE-79 within the Common Weakness Enumeration framework. This specific flaw resides in the videoEmbeded.php component of AVideo software and stems from an insufficient sanitization mechanism applied to user-supplied input. Specifically, the application processes the link parameter without implementing any form of encoding or escaping before incorporating it into the HTTP response. The technical root cause lies in how the server-side script handles this variable; rather than treating the input as plain text data that requires strict validation against a whitelist of allowed characters, the system directly interpolates the raw value into an HTML comment structure. This architectural decision creates a direct injection path for malicious actors to manipulate the client-side rendering context.
The operational mechanics of the exploit rely on breaking out of the intended HTML comment scope using standard delimiters. By injecting the sequence --> at the beginning of the link parameter, an attacker can effectively terminate the existing HTML comment block prematurely. This action shifts the browser's parsing mode from ignoring content to actively interpreting it as executable markup or script tags. Once this boundary is breached, any subsequent JavaScript code injected into the payload will be executed by the victim's web browser upon loading the crafted embed URL. Because the vulnerability is reflected rather than stored, the attack vector requires social engineering tactics where a user must be tricked into visiting a specially constructed URI hosted on or linked from a malicious site.
The impact of this vulnerability extends beyond simple script execution and encompasses significant risks to data integrity and confidentiality within the context of web application security. Successful exploitation allows an attacker to execute arbitrary JavaScript in the context of the vulnerable domain, which facilitates session hijacking through cookie theft, credential harvesting via keylogging scripts, or defacement of the user interface. Furthermore, this flaw can serve as a pivot point for more complex attacks such as Cross-Site Request Forgery (CSRF) amplification or phishing campaigns that mimic legitimate application interfaces to deceive users into revealing sensitive information. The lack of output encoding means there is no inherent defense against these client-side code injection attempts, leaving the user experience and security posture severely compromised.
From a defensive perspective, mitigating this vulnerability requires implementing strict input validation and robust output encoding strategies aligned with industry best practices such as OWASP guidelines. Developers should enforce a whitelist approach for the link parameter to ensure only expected URL formats are accepted, rejecting any input containing suspicious characters like angle brackets or semicolons before processing occurs. More critically, even if valid URLs are permitted, they must be properly encoded using context-specific output encoding techniques when rendered in HTML comments or other DOM elements. This ensures that special characters are converted into their corresponding entity representations, preventing the browser from interpreting them as structural markup. Additionally, deploying Content Security Policy headers can provide a layer of defense by restricting the sources from which scripts can execute, thereby limiting the impact if an injection attempt succeeds despite preventive measures.