The battery no longer works but I’ve kept it plugged in and used it for streaming music at work the last few years. Today it’s in an infinite loop of rebooting and I noticed the glass popped out!
The bulging battery on its own isn't (much) more dangerous than a normal one. The problem is once the device splits open, the battery is no longer protected and much more likely to get accidentally punctured. A regular battery combusts when punctured, and the bulging battery would vent that gaseous content (which IIRC is Hydrogen) and then combusts, which makes for a larger initial fireball.
I used to deal with puffed batteries a lot and went through some basic training on safety and how to ship devices with them for repair. We only ever had one battery fire, it was a from a normal battery, and it happened when someone shoved a t-pin through the headphone jack of an iPod touch because they thought it was a reset pinhole.