Cumulative Update for Windows 10 Version 1511 for x64-based Systems (KB3135173) installed on February 10 caused the following problem:
Affected file types: .jpg, .png
I use IrfanView and I want to keep using it. I'm highly dependent on it as it allows me to move/copy files quickly while viewing them.
Windows no longer allows to associate files with IrfanView. They are instantly reset.
Solution: I solved it by uninstalling the update and blocking it from reinstalling with this tool:
Edit March 2:
My plan was to sit this out, uninstall Cumulative Update and wait until Microsoft releases the next Cumulative Update, which I hoped wouldn’t exhibit the same glitch.
Today, Cumulative Update for Windows 10 Version 1511 for x64-based Systems (KB3140743) was rolled out. KB3140743 resets my defaults Photos defaults instantly and doesn’t let me change the default viewer under Settings > System > Default Apps. App defaults are silently reset and notifications in the Action Center are no longer issued.