Due to the recent POODLE vulnerability discovery, payment processors (starting with PayPal) have begun disallowing the use of (the industry standard version of) SSL v3, in order to protect everyone's financial safety.
Your customer may receive an error during checkout, like: "An error occurred when we tried to contact the payment processor. Please try again, select an alternate payment method, or contact the store owner for assistance. () - (35) error:1408F10B:SSL routines:SSL3_GET_RECORD:wrong version number"
This is an immediate and verified Zen Cart team approved fix. It is too soon to know if this fix will be permanent or whether a better fix will be coming in updated payment modules. In the meantime shops affected can be back up and running quickly.
You may not being using all of the payment modules so choose which payment method you need to have the fix applied to. Are you using a different payment method? Contact me and let me know.