Be common/public knowledge
Definition 1 of 1
Pro Tip 1/3General Truths
Use when expressing information widely accepted as true and not disputed within a community or culture. 
It's common knowledge among students that our library has the longest working hours.
Pro Tip 2/3Implicit Confirmation
Implies the listener also knows the fact, and it's unnecessary to verify the information. 
It's public knowledge that the company will merge, so there's no need to announce it.
Pro Tip 3/3Undermines Secrecy
Suggests that something intended to be secret is actually widely known. 
Despite the efforts to keep the recipe secret, it's common knowledge in the town.