Blog: If a form stopped working when you upgraded to v1.5.0+ ...

One of the things that changed in Zen Cart v1.5.0 was an additional security check to make sure that forms submitted via the POST method were coming from the active session.  This is great for the security of your store, but can have unintended consequences.  Essentially, if a form is sent to your site via POST that doesn't include a securityToken variable whose value matches the session-variable of the same name then that form is rejected and a redirect is performed to either the page_not_found (v1.5.0) or time_out (v1.5.1+) page.

This check can have unwanted result for some of your customizations, especially if those customizations code the HTML