Removing HTTP content from a listing

[double_e_warehouse]

I'm getting an alert that there's non-secure HTTP content in a listing. When I click on "See details" it gives me the names of two single pixel images in my item description. The description should only be text, so I don't know why those images would be in there and I don't see a way to remove them. I tried to follow the instructions on the Browser Security page, but they only seem to apply if you're bulk editing multiple listings and I've only got the one listing that's setting off the alert. Anyone know how to fix this?