Is there a word for a sentence that becomes false for having been said?

There exist some statements that become untrue simple because someone has said them publicly. A conceptual example might be I have never said the word: contumacious. A more realistic example might be 0QlmIfMjYFLUrCtBT8qd is a secure password.

These kinds of statements are probably not common, but is there any single word or phrase that can be used to describe them?

Answer

Such statements are called self-defeating.

Self-refuting ideas or self-defeating ideas are ideas or statements whose falsehood is a logical consequence of the act or situation of holding them to be true.
– wikipedia

A more general concept is defeasibility, where a defeasor ‘defeats’ a position (not necessarily its own). This is formalised in defeasible logic.

Attribution
Source : Link , Question Author : Duck Hunt Duo , Answer Author : Lawrence