uBlock Origin for Firefox addresses new first-party tracking method

[harlan4096]

The latest version of the content blocker uBlock Origin for the Mozilla Firefox web browser includes a new feature to detect a new first-party tracking method that some sites have started to use recently.

The issue was first reported ten days ago by user Aeris on the project's official GitHub page. Some sites started to use canonical name records (CNAMEs) to bypass filters used in content blockers. First-party resources, e.g. a subdomain, are not blocked usuall unless they are known to only serve advertisement.

The main issue from a content blocking perspective is that identification and detection is difficult. The extensions would have to uncloak alias hostnames in order to provide the user with information and the ability to do something about it.

Raymond Hill, the developer of uBlock Origin, found a way to address the new first-party tracking method in Mozilla Firefox.

Side-note: Why only Firefox? Because Mozilla has created DNS APIs that may be used to expose the CNAME while Google has not. For now, it is not possible to protect against this form of tracking in Google Chrome. Hill writes "Best to assume it can't be fixed on Chromium if it does not support the proper API".

Firefox users who upgrade to the latest version of uBlock Origin, may notice a new permission request (Access IP address and hostname information). This is required to unlock access to the DNS API in the browser extension.

Note: The version is currently available as a beta version. It may take some time before it becomes available to stable users (version 1.24 required)

Firefox users who run the extension need to do the following to set things up properly on their end:

1. Open the Settings of the extension, e.g. from about:addons or by clicking on the dashboard icon in the uBlock Origin interface.

2. Check the "I am an advanced user" box on the first page that opens.

3. Activate the settings icon next to the option to open the advanced settings.

4. Change the value of the parameter cnameAliasList to *.
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