I assume that you are talking about feedback.
I also assume that you looked at your feedback. The default is to show All Feedback which is the feedback left for you by the seller. To see what you left, you need to look at "Feedback left for others". There you will see the negative you left.
No security problem. Just a new buyer still learning how to use eBay. It will take time to gain experience.
Come to the forums and ask questions first without assuming something is wrong. Someone will know the answer or at least help you figure out what is going on.
PS This reply is not meant to criticize you but to help you.
