Bag of worms

When people say that something bad is like opening a can of worms, I wonder if they’ve actually opened a can of worms.
I don’t see cans of worms on Amazon to try for myself.
Do they come with pulltabs, or do you need a can opener?
And don’t worms need air? A sealed can would just be full of dead worms.
Instead, I’d think they’d be opening a canvas bag of worms.
Canvas allows some air to breathe through the fabric, but keep everything inside.
So, you open the can. Or bag.
It’s not like worms are dangerous, right?