I've just run the installer to upgrade from 2.3.1 to 2.8.1

Now when I try to go to the Control Panel (admin.php), I am redirected to


Which gives the "Disallowed Key Characters" error.

1 Answer 1


Turns out this is a known bug with 2.8.0+, affecting users with uri_protocol configuration setting set to ‘PATH_INFO’.

There is a patch available here:


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