τὰ γὰρ κρυφῇ γινόμενα ὑπ' αὐτῶν αἰσχρόν ἐστιν καὶ λέγειν·
1)From the NET Bible: "tn The participle τὰ . . . γινόμενα (ta . . . ginomena) usually refers to 'things happening' or 'things which are,' but with the following genitive phrase ὑπ᾿ αὐτῶν (Jup’ autwn), which indicates agency, the idea seems to be 'things being done.' This passive construction was translated as an active one to simplify the English style."
2) From Robertson's Word Pictures: "In secret (kruphēi). Old adverb, only here in N.T. Sin loves the dark.
Even to speak of (kai legein). And yet one must sometimes speak out, turn on the light, even if to do so is disgraceful (aischron, like 1 Co 11:6)."
3) κρυφῇ-"adv. in secret" (Grosvenor-Zerwick).