Hi,
Those weird letters are already attached by the "share" buttons (that are provided by addthis.com) for the uniqueness.
But there is a way to avoid it.
Open this PHP file:
/templates/YOUR_TEMPLATE/html/com_virtuemart/productdetails/default.php
(default.php or flexv2.php which ever layout you are using for product details page)
and find this line (around 251st line)
var addthis_config = {"data_track_addressbar":true};
replace it with this:
var addthis_config = {"data_track_addressbar":false};
The weird letters attached at end of the URL will be gone.
Regards,
Support.