Following message continuous logged 5-10 lines per second.
Log file size can exceed 1GB.
This was fixed with changes made shortly after the update launched. Thanks for the report!
Also, being in a public The Great Pug world for around 10 minutes caused this log message to be printed repeatedly in different variations 1930742 times:
*** Using existing fallback: '<something here>'
where "something here" is any of the following:
Legacy Shaders/Transparent/Cutout/Soft Edge Unlit
Standard (Specular setup)
VRChat/PC/Toon Lit (Double)
VRChat/PC/Toon Lit Cutout
VRChat/PC/Toon Lit Cutout (Double)
This seems to only get logged when at least one non-VR user is in the world. Another VR (full body) user did not cause this to happen but as soon as the non-VR user rejoined, the log file spamming continued.
Currently actively investigating.