Know every vulnerabilitybefore it knows you.
DevGuard continuously monitors your dependencies and alerts you when CVEs like this one affect your stack — with real-time threat intelligence built for developers.
GHSA-x369-mcw8-8rvj
No affected components available
Description
Dark Reader versions prior to 4.9.117 included a behavior where a website could request a style sheet from a locally running web server, for example http://localhost:8080/style.css, If an address was available and returned a text/css content type.
Patches
The problem was fixed in version 4.9.117, released on December 3, 2025. Most users received the update automatically. Users running manual builds must upgrade to version 4.9.117 or later.
The installed extension version number can be verified in Dark Reader's menu (More > All settings > About), browser settings, chrome://extensions or about:addons pages.
Users are encouraged not to disable automatic extension updates and use the latest browser version, as browser releases typically include multiple security fixes of varying severity.
NPM package
The issue does not affect developers using the darkreader NPM package for website integration. Developers using the setFetchMethod() API must ensure the cross-origin requests are restricted to the intended scope.
Custom forks
Developers using custom forks of earlier versions of Dark Reader to build other extensions, or integrating it into their apps or browsers, should review their implementation to ensure cross-origin requests are handled securely.
Acknowledgements
Security research performed by Brian Carpenter - Deep Fork Cyber.
The vulnerability can be exploited over the network without needing physical access. It is difficult for an attacker to exploit this vulnerability and may require special conditions. An attacker does not need any special privileges or access rights. The attacker needs the user to perform some action, like clicking a link. The vulnerability can affect other systems as well, not just the initial system. There is a low impact on the confidentiality of the information.
Limited exploitation activity has been observed. Close monitoring and planned remediation are recommended.
The exploit probability is very low. The vulnerability is unlikely to be exploited in the next 30 days.
We did not find any exploit available. Neither in GitHub repositories nor in the Exploit-Database.
Browse More
Continuously monitor your dependencies and get alerted when vulnerabilities like this one affect your stack.
Checkout DevGuard