My favorite was console control-characters accidentally embedded in plain text by cross-platform document code-page encoding errors. One learns over the years

My favorite was console control-characters accidentally embedded in plain text by cross-platform document code-page encoding errors. One learns over the years that every program stage/interface must sanitize input, sanity check formats, and isolate data on a per account log. Did the user intend "P=0/O" as a joke... we'll never know. =)