When apache2 is serving https using mod_ssl, and running with 'LogLevel debug', it frequently logs lines like this, followed by a hex dump:
ssl_engine_io.c(1882): OpenSSL: read 518/518 bytes from BIO#81b3928 [mem: 81b93f5] (BIO dump follows)
The hex dumps contain nothing that is visually recognizable as plaintext, i.e., no HTTP headers or anything like that, and no obvious repetition from one session to the next.
Do these dumps contain anything sensitive that an adversary couldn't already obtain by sniffing my network traffic? If I'm just looking at a bunch of ciphertext, that's fine. But if I'm looking at private keys, or session keys, or any precursor to them such as data from RAND_bytes(), then I need to do something about my logging level.