Firefox 75: Telemetry reports the default browser to Mozilla

[German]The just released Firefox 75 comes in the Windows version with a nasty surprise. A telemetry function transmits daily the used operating system as well as the standard browser to Mozilla.

I had just introduced the new version of the browser in the blog post Firefox 75 and 68.7.0esr released. Mozilla's developers had also diligently documented what the new browser can do. What I didn't notice while browsing the change logs is that new telemetry feature is on board.

With the release of Firefox 75, Mozilla has introduced a new executable and scheduled task that sends some basic operating system info, the current default browser, and the previous default browser every to their servers.

— BleepingComputer (@BleepinComputer) April 8, 2020

Bleeping Computer now points out in the above tweet to the 'by-catch' of Firefox 75. With this version, a new program file default-browser-agent.exe is shipped an will be stored into the folder:

C:\Program Files\Mozilla Firefox\

The portable version keeps this file in the directory::

FirefoxPortable\App\firefox64

The program collects telemetry data like the operating system version and which standard browser is used. The whole thing is transferred to Mozilla once a day.

Mozilla explains the approach

Mozilla has revealed the details in this blog post. With Firefox 75 for Windows, developers are launching a new telemetry feature in the form of a scheduled task. This should help the developers to understand changes in the default settings of the browser.

• The telemetry task collects information about the current and previous default browser settings of the system as well as the locale and version of the operating system.
• This data cannot be associated with regular profile-based telemetry data. If you are interested in the schema, you can find it here.
• The information collected by the task is sent to Mozilla as a background telemetry ping every 24 hours.
• The developers want to respect the user-configured telemetry opt-out settings stored in the last used Firefox profile.  
• In enterprise environments, the custom policy settings are evaluated in relation to enterprise telemetry (if they exist). The browser also respects the policies for specifically disabling this telemetry task.

The developers see the collection of telemetry data as a way to ensure that they can understand standard browser trends to improve Firefox.

The task in task planner

When Firefox 75 is installed as a browser on Windows, it sets up a task in the task planner that runs every 24 hours. The entry should be located in the Task Scheduler in the Task Scheduler Library/Mozilla branch.

The colleagues from Bleeping Computer have collected more details about this task in this post. Since I am only using the portable version of Firefox for testing here, I checked. This task does not exist on my system.

Turn off the telemetry

To prevent the collection of telemetry data, go to the burger menu with the three bars in the upper right corner of Firefox and select the menu command Settings. On the settings page, select the category Privacy & Security.

(Firefox Telemetry settings, Source: Bleeping Computer)

If you then scroll down the page, you will find the group Data collection by Firefox and its use. In my case, only Allow Firefox to install and run studies was marked. The option Allow Firefox to send data on technical details and interactions to Mozilla, which is responsible for telemetry, was disabled. This means that no telemetry data will be sent.

Group policies and more

Mozilla has introduced a Windows group policy that prevents the executable default-browser-agent.exe from sending telemetry data with the default browser information. To enable this policy, created the 32-bit DWORD value DisableDefaultBrowserAgent under the registry key:

HKEY_LOCAL_MACHINE\SOFTWARE\Policies\Mozilla\Firefox

and set it to 1. Bleeping Computer has ceated a reg file to import this setting.

Even if disabled via telemetry settings or group policies, the scheduled task will need to be removed manually to prevent it from continuing to run.

— BleepingComputer (@BleepinComputer) April 8, 2020

Bleeping Computer indicates that the telemetry data collection task is still being performed in the task planning. The entry in task scheduling must therefore be removed manually. The steps are described here.