This typically has to do with a new Facebook account setting for security as it relates to use of applications running inside of Facebook. Follow the steps below to check your secure browsing setting and disable secure browsing while you are inside of Facbeook.
1) Within your Facebook page click on the down arrow next to the “Home” option and choose Account Settings
2) Choose the Security option on the left rail
3) Make sure your secure browsing is disabled
As an important side note, this warning will not come up for stores that have their product images stored on a secure server with a dedicated SSL certificate.