Windows blocks apps from changing your default browser

Windows is generally flexible about tweaks to its system—and advanced users have long taken advantage of registry tweaks to make the OS behave. But recently, Microsoft has quietly barred access to one setting in Windows 10 and Windows 11, making a switch of your default browser only possible through the Windows settings app.




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As reported by Bleeping Computer, a new driver released during Microsoft’s February updates now locks down the registry, preventing any changes performed outside Windows settings. It was initially spotted by Christoph Kolbicz, an IT consultant and creator of two programs that allowed users to modify file associations and the default browser in Windows.

Windows currently relies on a particular kind of hash (that is, a conversion of text or even other data into a fixed-length combination of numbers and letters) to designate a program as a default app. Before the addition of this new driver, third-party apps could reverse-engineer the process of creating the hash to then swap in their own selection. Now they’re blocked from doing so—which users can reproduce themselves by attempting to manually edit the registry, as Bleeping Computer did. When attempting to change the value of the hash through the Registry Editor, an error message of “Cannot edit Hash: Error writing the value’s new contents” appears.




The error message that appears if you try to edit the hash entry in a Windows 10 registry.



The error message that appears if you try to edit the hash entry in a Windows 10 registry.PCWorld

The error message that appears if you try to edit the hash entry in a Windows 10 registry.PCWorld


PCWorld

While this updated approach to switching your default browser may seem draconian, it’s largely good news from a security perspective. Malicious apps will have a more difficult time trying to modify the default browser behind your back—meaning they can’t substitute a phony browser for your normal one, in order to potentially monitor and/or capture the details of your browsing sessions (including any forms you fill out). You’ll still need to practice safe online behavior and have antivirus software on your PC, but it’s one less potential attack vector.

Changing your default browser in Windows settings remains possible; just head to the default app settings within the app. If that’s still inconvenient (or philosophically vexing), determined users have since discovered a workaround this limitation—you can first disable the driver locking everything down, then disabling a scheduled task that automatically re-enables it. But the overwhelming majority of Windows users shouldn’t need go to such lengths.

As for the reason behind this update, Kolbicz speculates that it could relate to European regulations meant to guarantee fair competition between software companies. However, the driver also appears on Windows computers in the United States, which are not bound by such terms—and the new driver doesn’t seem to be enforcing the lock down uniformly yet. Bleeping Computer’s tests indicate that at least some Windows 11 PCs still allow registry changes to the default browser setting.

Security Software and Services, Windows