CVE-2026-19986 in Adblock for Youtube Extension
Summary
by MITRE • 08/17/2026
A weakness has been identified in Adblock for Youtube Extension up to 7.2.1 on Chrome. The impacted element is the function updateDynamicRules of the file contentscript.js of the component Event Listener. This manipulation of the argument yt-anti-adblock-detected causes improper authorization. It is possible to initiate the attack remotely. The exploit has been made available to the public and could be used for attacks. The vendor was contacted early about this disclosure but did not respond in any way.
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Analysis
by VulDB Data Team • 08/17/2026
The identified vulnerability resides within the Adblock for YouTube extension, specifically affecting versions up to 7.2.1 on the Chrome browser platform. This security flaw is located in the updateDynamicRules function contained within the contentscript.js file, which operates as part of the Event Listener component responsible for managing ad-blocking rules dynamically. The core technical issue stems from an improper handling of the yt-anti-adblock-detected argument passed to this function. Due to insufficient validation or sanitization mechanisms, the extension fails to properly authorize requests associated with this parameter, allowing malicious actors to manipulate the internal state of the ad-blocker logic. This misconfiguration effectively bypasses intended security controls within the extension's operational framework, leading to a breakdown in authorization protocols that are critical for maintaining the integrity of content filtering operations.
From an operational perspective, this vulnerability enables remote exploitation without requiring user interaction beyond visiting a targeted webpage or executing specific scripts. The lack of proper authorization checks allows attackers to inject malicious payloads or alter ad-blocking behaviors remotely. This can result in various adverse outcomes including but not limited to unauthorized data exposure, injection of deceptive content, or disruption of the browsing experience by forcing ads that should be blocked. Since the exploit has been made publicly available, the risk landscape is significantly elevated as threat actors with varying levels of expertise can leverage this code for automated attacks against users running vulnerable versions of the extension. The absence of vendor response to early disclosure attempts further exacerbates the situation, leaving a prolonged window of exposure where systems remain unprotected against known exploitation techniques.
In terms of industry standard classifications, this vulnerability aligns closely with CWE-287 Improper Authentication and potentially CWE-94 Cross-Site Scripting if the manipulated argument leads to code injection scenarios depending on how the yt-anti-adblock-detected value is processed within the DOM or script execution context. Furthermore, from a tactical standpoint as defined by MITRE ATT&CK, this flaw facilitates techniques related to Initial Access and Execution through browser extensions which are often trusted components that can be abused for persistent access or data exfiltration. The exploitation of extension vulnerabilities represents a significant attack vector because users typically grant extensive permissions to such tools under the assumption they enhance security rather than compromise it.
Mitigation strategies must prioritize immediate remediation given the public availability of exploits and the lack of vendor patches. Users should immediately disable or uninstall the Adblock for YouTube extension until an updated version addressing this authorization flaw is released by a reputable alternative provider. System administrators managing enterprise environments should enforce policies that restrict the installation of unverified extensions via Chrome Enterprise policy controls to prevent exposure across organizational endpoints. Additionally, implementing Content Security Policy headers and monitoring browser console logs can help detect attempts to exploit similar vulnerabilities in other components. Long-term resilience requires adopting an extension whitelist approach where only audited and regularly updated security tools are permitted, thereby reducing the attack surface associated with third-party script execution within the browsing context.