[zwegner]

> If exceptions are being logged with any level of detail, and an attacker has the ability to provoke exceptions while varying error message content, then the thing that seems safe was just made quite unsafe.

Right, I would certainly include that in "user data" though. I was mainly responding to the idea that using two logging libraries is strictly worse than one: when log4j is only used for logging safe data, and another library elsewhere, this is better than using log4j everywhere.