Re: Wired lav capsule leak
Batteries can leak at any time, without much warning. It happens. It's good practice to remove them if the equipment isn't being used for any period, but isn't always practical.
When they do leak, the best you can do is clean out as much of the material as possible. If you can open up the device, it's even better, as you can get in and clean more out. Usually the damage isn't too severe, although it can cause certain plastics to erode or warp. Metal can usually be cleaned, although it may then be more susceptible to corrosion in the future, so keep an eye on the contacts.
If you only spent $50 on the mic, it's not an end of the world loss if it dies on you.