CVE-2026-17739 in Chrome
Summary
by MITRE • 07/30/2026
Insufficient policy enforcement in Extensions in Google Chrome prior to 151.0.7922.72 allowed an attacker who convinced a user to install a malicious extension to inject arbitrary scripts or HTML (UXSS) via a crafted Chrome Extension. (Chromium security severity: Medium)
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Analysis
by VulDB Data Team • 07/30/2026
This vulnerability represents a critical weakness in chrome's extension security model that enabled unauthorized script injection through malicious extensions. The flaw existed in chrome versions prior to 151.0.7922.72 where the browser failed to properly enforce security policies governing extension behavior, creating an attack surface that could be exploited by malicious actors. The vulnerability specifically targeted the extension installation and execution process, allowing attackers to craft extensions that could bypass chrome's built-in security mechanisms and execute arbitrary code within the browser environment.
The technical implementation of this vulnerability stemmed from inadequate validation of extension content and insufficient sandboxing controls during the extension lifecycle. When users installed malicious extensions, the browser would not properly verify the extension's integrity or enforce strict security boundaries between the extension and the browser's core functionality. This weakness enabled attackers to inject cross-site scripting payloads that could execute within the context of legitimate websites, effectively creating a universal cross-site scripting vector. The attack leveraged the trust model between chrome and its extensions, where legitimate extensions were granted elevated privileges that could be abused by malicious actors.
The operational impact of this vulnerability was significant as it allowed attackers to perform unauthorized actions across multiple websites without requiring user interaction beyond initial extension installation. Once installed, the malicious extension could inject scripts into web pages, potentially stealing session cookies, performing unauthorized transactions, or redirecting users to phishing sites. The medium severity classification by chromium reflects the specialized nature of the attack vector, which requires user consent for extension installation but can then operate with elevated privileges within the browser environment. This vulnerability particularly affected users who installed extensions from untrusted sources or were deceived into installing malicious software.
Mitigation strategies should focus on immediate chrome updates to version 151.0.7922.72 or later where the security flaws have been addressed through enhanced extension validation and stricter enforcement of security policies. Organizations should implement comprehensive extension management policies that restrict installation permissions and regularly audit installed extensions for suspicious behavior. Users must be educated about the risks of installing extensions from untrusted sources and should only install extensions from official chrome web store. The vulnerability aligns with CWE-284 access control weaknesses and maps to ATT&CK technique T1176 for bypassing user execution restrictions through extension manipulation, highlighting the need for layered security approaches that combine automated patching with user awareness training.