I have domain masking turned on through my domain registrar so that it always displays foo.org in the address bar. I just discovered that after my customers sign up via PayPal, and they are returned to my site along with POST data for my site to process, variables are automatically appended to the URL like this:
foo.org/success.php?txn_id=kb0099898yp&txn_status=sdlkfjbsdkljfbsdkjb&etc.
Trouble is, these variables remain in the address bar indefinitely, even if they click on a link and another page loads! If they refresh the page, no matter where they go on my site after this, it resubmits the data to my server for processing!
This also happens if the customer manually appends anything to the URL. It never goes away.
I have looked all over SO and Google, and I'm either not asking the right question, or no one else has had this problem before :)
How do I remedy this?