Why has Wonder Woman never had a wardrobe malfunction with her corset?
In addition to all the other answers, I want to say that it is evidence that you have never had much experience with corsets. As someone who has extensive experience with women wearing corsets, if they are properly put on, it is not easy to have a “wardrobe malfunction” in that, good luck getting a breast to pop out, even if you’re trying. Those thing are tight and if they are fitted properly, aren’t going to shift much at all.
What’s more, while most corsets tend to flatten the breasts, Wonder Woman’s tend to shape around them, making the likelihood of them popping out even more unlikely. I suggest, if you are not a woman, try assisting a (consenting) woman in taking them on and off at some point. You’ll see that they aren’t just going to pop off.
That’s on top of the fact that she is basically a magic god and it would be trivial for her to not have her clothing fall off.
What is Wonder Woman’s weakness?
The first is that while she is durable enough that most bludgeoning and some slashing weapons don’t do much to her, piercing weapons completely bypass her resistance meaning it only takes one well placed bullet to kill her (Assuming she doesn’t stop it with one of her bracelets.
The second is that if she were to break any of her godly gifts (breaking the lasso of truth, snapping her sword in half, melting her crown) she has all of her powers stripped from her and is left completely mortal as well as rapidly aging her.