Google auth is broken on current `stable`. Best guess is due to recent PhutilURI changes in rPHU.
Looking at network requests, I see:
1. https://phabricator.[CENSORED].com/ 302 GET
Location: https://accounts.google.com/o/oauth2/auth?client_id=[CENSORED].apps.googleusercontent.com&scope=email%20profile&redirect_uri=https%3A%2F%2Fphabricator.[CENSORED].com%2Foauth%2Fgoogle%2Flogin%2F&state=[CENSORED]&response_type=code
2. https://accounts.google.com/o/oauth2/auth?client_id=[CENSORED].apps.googleusercontent.com&scope=email%20profile&redirect_uri=https%3A%2F%2Fphabricator.[CENSORED].com%2Foauth%2Fgoogle%2Flogin%2F&state=[CENSORED]&response_type=code 302 GET
Location: https://phabricator.[CENSORED].com/oauth/google/login/?state=[CENSORED]&code=[CENSORED]&scope=email+profile+https://www.googleapis.com/auth/userinfo.profile+https://www.googleapis.com/auth/userinfo.email
3. https://phabricator.[CENSORED].com/oauth/google/login/?state=[CENSORED]&code=[CENSORED]&scope=email+profile+https://www.googleapis.com/auth/userinfo.profile+https://www.googleapis.com/auth/userinfo.email 302 GET
Location: https://phabricator.[CENSORED].com/auth/login/google:google.com/
4. https://phabricator.[CENSORED].com/auth/login/google:google.com/ 500 GET
Unhandled Exception ("Exception")
The authentication provider did not return a client state parameter in its response, but one was expected. If this problem persists, you may need to clear your cookies.
Version information from https://phabricator.example.com/config/version/:
* phabricator e6331ca8efc1f60e38f9ca13dc292f9bb00ea104 (Mon, Feb 25) (branched from 701a9bc339b9d419326a62e85ef13666b08046cd on origin)
* arcanist b4a302683b1aefbbb2ab9d1aaaf418b551b84b28 (Sat, Feb 23) (branched from 9581dd0f52726b10c923038c28d5fe2170f0d1b6 on origin)
* phutil 813a26a2d09758f3c407a0c99c6761f11f62cb90 (Sat, Feb 23) (branched from 671ec8fb8f7aa74e9e825ca95fd96ce4bbf79160 on origin)