RSCS is a condition which causes a person to reveal a highly personal secret or factoid without provocation to another with whom they are not formerly acquainted in order to relieve the guilt complex accompanied with harbouring said secret/factoid. Most often, this takes place during innocuous social interaction, such as a client/clerk rapport, waiting at a transit stop or in line at a government services office.
A typical scenario where Random Stranger Confidence Syndrome is exhibited:
Commuter #1: Excuse me, do you have the time?
Commuter #2: It is 8:23. The bus is running a little slow today.
Commuter #1: Damn, I'm going to be late for work. I should have called in sick today and stayed home with the nanny to carry on our illicit affair. My wife would kill me if she ever found out.
Commuter #2: Oh look, here comes the bus. Nice chatting with you!