Extensions install must be disabled.

Overview

Finding ID	Version	Rule ID	IA Controls	Severity
V-64891	DTBF186	SV-79381r2_rule		Medium

Description
A browser extension is a program that has been installed into the browser which adds functionality to it. Where a plug-in interacts only with a web page and usually a third party external application (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 which apply to web pages. For example, a Chrome 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 extension then plug-ins can be loaded and installed from malicious sources and used on the browser.

Description

A browser extension is a program that has been installed into the browser which adds functionality to it. Where a plug-in interacts only with a web page and usually a third party external application (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 which apply to web pages. For example, a Chrome 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 extension then plug-ins can be loaded and installed from malicious sources and used on the browser.

STIG	Date
Mozilla Firefox Security Technical Implementation Guide	2017-12-21

Details

Check Text ( C-65575r1_chk )
Open a browser window, type "about:config" in the address bar, then navigate to the setting for Preference Name "xpinstall.enabled" and set the value to “false” and locked. Criteria: If the value of “xpinstall.enabled” is “false”, this is not a finding. If the value is locked, this is not a finding.

Fix Text (F-70831r2_fix)
Set the preference “xpinstall.enabled” to “false” and lock using the “mozilla.cfg” file. The “mozilla.cfg” file may need to be created if it does not already exist.