Title

Firefox must be configured to disable the installation of extensions. (Cat II impact)

Discussion

A browser extension is a program that has been installed into the browser to add functionality. Where a plug-in interacts only with a web page and usually a third-party external application (e.g., Flash, Adobe Reader), an extension interacts with the browser program itself. Extensions are not embedded in web pages and must be downloaded and installed in order to work. Extensions allow browsers to avoid restrictions that apply to web pages. For example, an extension can be written to combine data from multiple domains and present it when a certain page is accessed, which can be considered cross-site scripting. If a browser is configured to allow unrestricted use of extensions, plug-ins can be loaded and installed from malicious sources and used on the browser.

Check Content

Type "about:policies" in the browser address bar. If "InstallAddonsPermission" is not displayed under Policy Name or the Policy Value is not "Default" "false", this is a finding.

Fix Text

Windows group policy: 1. Open the group policy editor tool with "gpedit.msc". 2. Navigate to Policy Path: Computer Configuration\Administrative Templates\Mozilla\Firefox\Addons Policy Name: Allow add-on installs from websites Policy State: Disabled macOS "plist" file: Add the following: <key>InstallAddonsPermission</key> <false/> Linux "policies.json" file: Add the following in the policies section: "InstallAddonsPermission": { "Default": false }

Additional Identifiers

Rule ID: SV-251557r879587_rule

Vulnerability ID: V-251557

Group Title: SRG-APP-000141

Expert Comments

CCIs tied to check.

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