Not the only thing hack means now, or the most common usage anymore. See "life hack" - it means unexpected technique.

But this isn’t an unexpected technique it’s literally the core design of the pdf format. It’s a layered format that preserves the layers on any machine. Adobe has a redaction feature to overcome the default behavior that each layer can be accessed even if there is a top layer in front.

It's also the meaning used in the title of this very Web site.