Please upgrade here. These earlier versions are no longer being updated and have security issues.
HackerOne users: Testing against this community violates our program's Terms of Service and will result in your bounty being denied.
Localhost advice
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You won't be able to test in local host easily, as paypal has to be able to notify you.
Consider using something like localtunnel:
http://progrium.com/localtunnel/
It works pretty well.
grep is your friend.
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