For a trunk changeset leading up to Unity 2018.3.0a1 I used the Editor to make the simple project (see attached). In Play mode with Rift HMD when I look up or down the camera rotates around my original viewing vector rather than (or maybe in addition to) panning up or down).

This bug occurs in all three stereo modes. If I replace Oculus with OpenVR in the VR SDK list in Player settings and enter Play mode with the Rift HMD, the problem still occurs.

This is a regression. Using the same hardware I do not see the problem when I try Unity 2018.2.0b1.