Hello @panzi, are you still experiencing this issue on an up to date system?
I'll tell you the next time there's a Steam Client update.
Closing as this issue appears to have been resolved some time ago.
Ok, there just was a new steam client update that had a link in the changelog. Clicked that link -> the bug is still there.
Pressing Alt+Left did navigate back, though.
Nothing extracted yet.
Clicking a link in the steam changelog opens the link inside the small changelog window instead of the steam or desktop browser. You then can't navigate back to the changelog and the opened page in the tiny changelog window is not very usable. See the screenshot.