After today's update to 126.96.36.199, editors can not switch from en.wiki to other projects. User:Blackfish reported that he was unable to switch to his local pl.wiki; I have the same issue - can't switch to en.wikisource, en.wiktionary, or commons. An error message pops up that says, in relevant part:
- Could not load file or assembly 'Newtonsoft.Json, Version=188.8.131.52, Culture=neutral, PublicKeyToken=30ad4fe6b2a6aeed' or one of its dependencies.
This is absolutely critical to countless tasks and needs fixing immediately.