Accessing Login page shows You are not authorized to access this page Till about an hour ago my Drupal 7 site was working fine. But now when I access the login page (/user) I get an You are not authorized to access this page

So I checked the node_access table and I see a record for anonymous users - 0 0 all 1 0 0

I checked the sessions table and it didn't seem to be corrupted. But nevertheless cleared the records. But I am still unable to access the login page

The last time we applied a module update was 10 days back so I don't think its got to do anything with the module code written by us. 

I am at my wits end! Have anyone of you faced a similar issue?

EDIT 21st Oct 2014 : A link that explains the exploit - is here
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