CVE-2026-13957: Chrome Extension Security UI Flaw Enables UXSS Attacks

Technical summary

The vulnerability stems from an incorrect security UI implementation in Chrome's Extension mechanism. Extensions in Chrome operate with elevated privileges and can interact with web content in ways normal scripts cannot. The flaw allows a malicious extension to bypass security boundaries and inject arbitrary scripts or HTML into pages the user visits, achieving UXSS. The issue is classified as CWE-79 (Improper Neutralization of Input During Web Page Generation). The attack surface is limited by the CVSS metrics: an attacker needs network access, must craft a specific HTML page, and crucially must achieve user interaction both to install the extension and to visit the crafted page. The Chromium project assigned this a Medium severity rating reflecting the multi-step nature of the attack.

Business impact

While the CVSS score of 4.2 reflects a measured risk, the business impact depends on target context. For consumer-focused organizations, the risk is generally low because users must consciously install an extension and visit an attacker-controlled page. For enterprise environments where extension deployment is centrally managed, the risk is similarly contained—malicious extensions would need to bypass organizational controls. However, if an organization relies on third-party extensions or allows users broad extension installation freedom, this represents a session-hijacking vector that could lead to credential theft, data exfiltration, or account takeover. The integrity and confidentiality impact is confirmed; availability is not affected.

Affected systems

Google Chrome versions prior to 150.0.7871.47 are affected. This includes all earlier minor and patch versions. Chrome's auto-update mechanism means most users will receive the patched version automatically, but organizations with update management policies, off-network systems, or deferred rollout schedules should verify their fleet's current version. Desktop and mobile versions of Chrome are potentially affected; verify the specific version numbers in your environment.

Exploitability

Exploitation requires user interaction at two critical junctures: extension installation and visiting a crafted webpage. This two-step requirement significantly reduces opportunistic exploitation. An attacker would need to either compromise a legitimate extension distribution channel, create a convincing social engineering campaign, or rely on users who install extensions from untrusted sources. Once a malicious extension is installed, the attacker gains a persistent foothold with each subsequent page visit. The attack is not wormable and does not propagate automatically, limiting its scope to deliberately targeted users or campaigns.

Remediation

Update Google Chrome to version 150.0.7871.47 or later. For most users, Chrome's auto-update mechanism will deliver the patch automatically; verify completion by checking Settings > About Chrome. Organizations should prioritize rollout to systems where users have broad extension installation permissions or where third-party extensions are heavily relied upon. Additionally, enforce extension management policies that restrict installation to approved lists and block installation from unknown sources. Educate users about the risks of installing extensions from untrusted origins.

Patch guidance

Verify that your Chrome installation is at version 150.0.7871.47 or higher by navigating to Settings > About Chrome, which will also trigger an automatic update check. For enterprise deployments, use your MDM/mobile device management or centralized update service to confirm rollout completion. If you manage extension policies via G Suite or similar services, audit your approved extension list and remove any extensions of questionable origin or that are no longer in use. There are no known breaking changes associated with this security patch; standard update procedures apply.

Detection guidance

Monitor for suspicious extension installations within your environment, particularly those from unknown publishers or with unusual permission requests (especially content-script permissions). Review browser extension logs and policies to identify unexpected or unapproved extensions. If you suspect a malicious extension has been installed, isolate the system, remove the extension, clear browser data and cookies, and reset any compromised passwords. Network-level detection is limited, but behavioral indicators such as unexpected API requests or data exfiltration from browser processes may signal compromise. Ensure your endpoint detection and response (EDR) tools monitor for malicious script injection events.

Why prioritize this

Although the CVSS score is 4.2 (Medium), remediation should be prioritized routinely rather than as an emergency. The vulnerability requires user interaction and intentional extension installation, making it a lower-priority update than remote code execution flaws. However, it should be patched within your standard patching cycle—typically within weeks of release—because UXSS enables persistent session hijacking and credential theft if a malicious extension is installed. Organizations with heavy extension reliance or permissive installation policies should expedite patching. This is not a 'drop everything' vulnerability, but it is not a candidate for deferral.

Risk score, explained

The CVSS 3.1 score of 4.2 reflects several mitigating factors: the attack vector is network (AV:N), but the attack complexity is high (AC:H) because the attacker must craft a specific scenario and convince the user to both install an extension and visit a page. Privileges are not required (PR:N), but user interaction is essential (UI:R). The impact scope is unchanged (S:U), meaning the vulnerability does not break out of the browser context. Confidentiality and Integrity are impacted (C:L, I:L), but Availability is not (A:N). The overall score reflects a real but limited-scope risk; the multi-step social engineering requirement is the primary limiting factor.

Frequently asked questions