I have got the same problem as @Tanner. I'm running the version 0.5.2, disabled all plugins, restarted nodebb and cleared cache.
I even tried a git reset --hard HEAD, but not all "save" buttons works in the ACP. It seems to actually works in core options and some plugins, but not in many plugins settings like Facebook SSO, Steam SSO, Twitter SSO, Blog Comments.
Any idea what could cause this?