we need a 'secure escape' sequence that disables all subsequent escapes until rescinded!
And it can change the background colour of the affected lines to a shade unrepresentable by unprivileged sequences.
Mostly tongue-in-cheek, but... one of these years I'm going to track down what the heck the 'PRIVACY MESSAGE' sequence is actually for. ECMA48 is infuriatingly vague, and nothing seems to actually use or support it.
