The recent HTC One software update was been welcomed with open arms in thanks to its LTE connectivity fixes and overall improved performance. Unfortunately, the welcomed fixes brought about one negative change with the accidental removal of the HDR functionality from the camera app. Have no fear however as HTC worked fast and managed to push out a fix that’s now available Settings > About > Software Updates > Check now. Ultimately, this shouldn’t have happened in the first place but I’ll still give HTC a small round of applause for the quick 48 hour turnaround.
Keep an eye out for the fix.