Recently, I replied to a forum post with a GIF image and it worked just fine at first. The image appeared and all that. But after some time, the image just stopped working and showed plain HTML. I thought "Hey, that's odd. It's just a LOTR title card!" and tried to fix it by editing it, but it won't edit. Neither I can remove it.

I just want to know. Are we, normal users, allowed to use Images by using Markdown or is there some kind of vulnerability problem with it?