My son's Xbox controller is leaking blue liquid but still works. Is this dangerous? What...

Stop using and request a call back from support immediately

I don't think there is anything inside the series controllers that leaks blue (have many open and repaired them, where I work we are partnered with Microsoft for repairs), there is a couple of capacitors but even then not enough in them to leak. I suspect it has had something spilt on it and then cleaned off and the kid is saying its leaking. or they are using dodgy batteries that just need removing and cleaning up as that wouldn't be covered under repair anyway.

I wouldn't use a piece of electronics that is leaking any kind of liquid. I would unplug it and report it to MS support. You don't know what that liquid is, so it could leak into an area of the console that causes it to short out and it's really not worth
the risk to carry on using it IMO.

Even if it doesn't seem to affect the performance of your console, I wouldn't even have it plugged in. It's damaged, and by having it on, there are many risks involved. Even though it would be hard for me, I wouldn't touch the console until you get your
replacement console.

Hey TheTTechsan,

If the service centre can't repair the console you'll be sent a replacement at no extra charge or free if in warranty, so rest assured the issue will be fixed after you sent it to us for repair,

As far as I'm aware this isn't a known defect that loads of users are current having,

I hope this helps

FIZZY LP