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V-251554

CAT II (Medium)

Firefox must be configured to prevent JavaScript from moving or resizing windows.

Rule ID

SV-251554r1067554_rule

STIG

Mozilla Firefox Security Technical Implementation Guide

Version

V6R7

CCIs

CCI-000381

Discussion

JavaScript can make changes to the browser's appearance. This activity can help disguise an attack taking place in a minimized background window. Configure the browser setting to prevent scripts on visited websites from moving and resizing browser windows.

Check Content

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

If "Preferences" is not displayed under Policy Name or the Policy Value does not include "dom.disable_window_move_resize" with a value of  "true" and status of "locked", 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\
Policy Name: Preferences
Policy State: Enabled
Policy Value:
{
  "dom.disable_window_move_resize": {
    "Value": true,
    "Status": "locked"
  }
}

macOS "plist" file:
Add the following:
<key>Preferences</key>
<dict>
  <key>dom.disable_window_move_resize</key>
  <dict>
    <key>Value</key>
    <true/>
    <key>Status</key>
    <string>locked</string>
  </dict>
</dict>

Linux "policies.json" file:
Add the following in the policies section:
"Preferences": {
  "dom.disable_window_move_resize": {
    "Value": true,
    "Status": "locked"
  }
}