Firefox must be configured to not automatically update installed add-ons and plugins.

Severity	Group ID	Group Title	Version	Rule ID	Date	STIG Version
medium	V-251549	SRG-APP-000141	FFOX-00-000005	SV-251549r960963_rule	2025-02-11	6

Description
Set this to false to disable checking for updated versions of the Extensions/Themes. Automatic updates from untrusted sites puts the enclave at risk of attack and may override security settings.

ℹ️ Check
Type "about:policies" in the browser window. If "ExtensionUpdate" is not displayed under Policy Name or the Policy Value is not "false", this is a finding.

✔️ Fix
Windows group policy: 1. Open the group policy editor tool with "gpedit.msc". 2. Navigate to Policy Path: Computer Configuration\Administrative Templates\Mozilla\Firefox\Extensions Policy Name: Extension Update Policy State: Disabled macOS "plist" file: Add the following: <key>ExtensionUpdate</key> <false/> Linux "policies.json" file: Add the following in the policies section: "ExtensionUpdate": false

✔️ Fix

Windows group policy: 1. Open the group policy editor tool with "gpedit.msc". 2. Navigate to Policy Path: Computer Configuration\Administrative Templates\Mozilla\Firefox\Extensions Policy Name: Extension Update Policy State: Disabled macOS "plist" file: Add the following: <key>ExtensionUpdate</key> <false/> Linux "policies.json" file: Add the following in the policies section: "ExtensionUpdate": false