I have rooted my HTC One M8 running Android 4.4.3 (using this method). The process went fine and I did not have any hiccups. One of the main reasons I rooted my phone was I wanted to utilize AppOps, however have been quite unsuccessful on this front.
I have installed xPosed Framework Installer (this is the correct version for Android 4.4.3), however when I load the application I encounter the error:
app_process version "58" has been installed previously but version "--" was found now. If you did not expect an old file to be restored, you may want to try installing via recovery (auto or manual)
Now according to few threads, for the use of the HTC One you need to proceed through this in recovery mode (Reddit) - I have not tested this method yet as I want to investigate.
Are there any other methods we need to try, that we're aware of? The only concern I have is not to soft-brick my phone as I am unsure how to perform a recovery (I could learn but would prefer to do this with a working phone!)
I uninstalled Xposed and attempted a re-install, and now it appears as though I have lost ROOT access on my HTC One M8. I will reattempt to root my device to see what happens and if this in fact was the cause of my issue with Xposded.