Steps to reproduce: 1) In Aurora 45 for Android, open a page with a lot of links like https://www.reddit.com/ 2) Pinch to zoom in and out a few times 3) Tap or long-tap on a link or image Expected results: The link is highlighted while the tap is in progress. Actual results: Sometimes a different element on the page is highlighted. If you tap at different locations in sequence without changing the zoom level, the highlighted element is always offset in the same direction from the tap, as though it's converting screen coordinates into page coordinates using the wrong zoom or scroll translation. Doing another pinch zoom gesture sometimes changes the behavior to be correct, and sometimes just changes the offset to be different. Tested in Firefox 45.0a2 (2015-12-19) on a Moto X running Android 5.1.

If it's happening on Aurora 45 it's not APZ-related, since APZ is only enabled on nightly. This must have regressed in non-APZ code.