QQ space showed that a deceased friend checked my post. I was surprised and confused, what happened?

There are several possibilities for this: first, the "deceased" is false (this means that you are just friends on the Internet, and the source of the information about "deceased" has not been confirmed); the second is Someone (a close person knows the password) used his (her) account to log in; the third way is that his (her) account has been stolen (the thief does not know that the account owner is deceased)!