While I was testing the shopping cart setup I found that after I had made the purchase through PayPal it gave me the option to go back to my site, but then when I was testing another product / shipping I learned that I was still logged in to PayPal. In other words, after the 1st sale was completed the program didn't log me out of PayPal after I left the shopping cart.

Many users wouldn't know to shut down their browser after making a purchase and would just continue on to whatever site interested them. Doesn't this pose a security problem for the consumer and his / her PayPal account?

I can't see how that would cause any security concerns. After 5 minutes of inactivity, PayPal would require that user to log in again anyways.

Oh yeah... good point!