I've been using Joomsef with the paid extension for some time and recently have gotten several complaints of incorrect user information posting during checkout causing one user to see another's information, and the checkout progress bar was broken as well causing incorrect redirects. Fortunately this problem was solved promptly and can be fixed by adding the following without quotes to custom non-sef variables in the Joomsef extension manager: "index.php?page=checkout.index&" please be sure to include this in future releases by default as this has caused major problems for us and we found several other users with the same problem.

Hello,

thanks for your post and detail information on the problem.
We have already solved this problem in the one of the latest VirtueMart JoomSEF extension versions. (.11 or .12)
So, make sure you are using the latest one.

Also make sure, that after upgrade, the "wrong" URLs containting the string mentioned by you get purged.