A slip of the pen/tongue

Pro Tip 1/3

Accidental Disclosure

Used when someone accidentally reveals information that was supposed to be confidential or private.

He mentioned the surprise party; it was a slip of the tongue.

Pro Tip 2/3

Writing Corrections

Refers to minor mistakes while writing, often amended through editing or proofreading.

Erroneously writing '2012' instead of '2021' was a slip of the pen.

Pro Tip 3/3

No Harm Intended

Suggests the mistake was unintentional and the speaker or writer did not aim to offend or confuse.

It was a slip of the tongue when I used your old title; I meant no disrespect.