SQL Vulnerability in coupon input field

Hello,
I found an annoying security hole. Has a redeemed coupon and an expired one, such as BLACKFRIDAY. 
When you add a simple operator to the coupon code in combination with quotes, you can reactivate this coupon an unlimited number of times (each time adding a space so that the combination does not repeat). I do not want to post an injection example, if interested, I will send it to the administrator at the mail indicated by him.
Sincerely.

Please could you send details to martin at remository dot com as I'm working on an updated version of user points.

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