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V-251553

CAT II (Medium)

Firefox must be configured to block pop-up windows.

Rule ID

SV-251553r960963_rule

STIG

Mozilla Firefox Security Technical Implementation Guide

Version

V6R7

CCIs

CCI-000381

Discussion

Pop-up windows may be used to launch an attack within a new browser window with altered settings. This setting blocks pop-up windows created while the page is loading.

Check Content

Type "about:policies" in the browser address bar.

If "PopupBlocking" is not displayed under Policy Name or the Policy Value is not "Default" "true", this is a finding.
If "PopupBlocking" is not displayed under Policy Name or the Policy Value is not "Locked" "true", this is a finding.

"PopupBlocking" "Enabled" may be used to specify an allowlist of sites where pop-ups are desired, this is optional.

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\Popups
Policy Name: Block pop-ups from websites
Policy State: Enabled

Policy Name: Do not allow preferences to be changed
Policy State: Enabled

Optional:
Policy Name: Allowed Sites
Policy State: Enabled
Click "Show..." and enter a list of websites to be allowlisted.

macOS "plist" file:
Add the following:
<key>PopupBlocking</key>
  <dict>
    <key>Allow</key>
    <array>
      <string>http://example.mil</string>
      <string>http://example.gov</string>
    </array>
    <key>Default</key>
    <true/>
    <key>Locked</key>
    <true/>
  </dict>

Linux "policies.json" file:
Add the following in the policies section:
"PopupBlocking": {
      "Allow": ["http://example.mil/",
                "http://example.gov/"],
      "Default": true,
      "Locked": true}