Simple Syrup Is Seeping

I thought putting the full cup of simple syrup, which I made by boiling a cup of sugar in a cup of water, into a smaller plastic container instead of the larger one, would suffice.  All of the simple syrup fit, but when I put the lid on, I could see the syrup push up against the bottom of the lid, you know what I mean?

I put it in the fridge and didn't think anything more of it.  But when I opened up the refrigerator door later to get something to drink, I saw that there were droplets on the side and all around the container.  The syrup was seeping out.  I don't think the container was leaking, but I surmised that the lid pushed the syrup through any opening between the lid and the container, and if it didn't drip over the side of the container it was, um, solid enough that it could travel to the lip of the lid and then drop onto the glass shelf.

Darn.  I'm not one to clean the fridge, and now it's all sticky.  I actually poured out a little simple syrup so it wouldn't push up against the lid.  I also used, like, 15 mL of it on a, I think, gimlet.  But it continues to leak out.  I have put a paper towel underneath the collect the drops, but that's too late for the simple syrup that had dropped onto the shelf.  Meanwhile, I thought I would have used more of the syrup by now, but it doesn't look like I'll be using it at all this weekend.  So the simple syrup will continue to seep.