Don’t you dare steal my idea!
Too afraid to reveal your idea to the world because you think someone will steal it?
Too late!
Someone already has.
Or rather, you stole your idea from someone else.
That is the thing about ideas, they are “of their time” meaning that the same idea will occur independently multiple times when the time is right.
And there is nothing you can do (legally) that will prevent someone else from arriving at the same idea.