Steps to reproduce:
1. Login to http://docs.moodle.org/22/en/ as an ordinary user (not an admin)
2. Go to any unprotected page and click the edit tab
Rather than being able to edit the page, you are redirected to the log in page (though you remain logged in).
This problem affects 22/en, 20/en and 19/en (but not 21/en).