Scenario 1
Your board is currently 7.3 to 7.5.5 version
and
you _JUST_ want to patch.
go to members area and download the patch for your board and simply upload those files and you are done
Scenario 2
Your board is currently 7.0 to 7.5.5 version
and
you not only want to patch, but you really want to upgrade to latest version.
go to members area and download the full install of the latest 7.5.6p and run the upgrade.php script.
you are now not only upgraded, but you are _ALSO_ patched.
Scenario 3
Your board is 7.5.6 latest version ( not patched )
and
you want to just be safe and get patched
go to members area and download the patch for 7.5.6p and simply upload those files and you are done
That's all the scenarios
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SD