I have just upgraded and now getting this error when trying to login from the customer screen "There was a security error when trying to login"
Zen Cart™ v1.3.8 has an added security feature to prevent spoofed external logins. A "security token" field has been added to all login forms. This token must be current (not expired), and must be submitted with login username+password in order for logins to work properly.
If you have customized template "login" files, the new security features need to be merged into your customized template files.
The following files are affected:
And if you're encountering it in your Admin area, this file is affected as well:
Additionally, if you have customized your /includes/functions/sessions.php file for some reason, you'll also need to merge the new changes for this core file into your customized version.