When a piece of illusory knowledge spreads to epidemic proportions and turns into common knowledge, bubbles and panics can result.
It is common knowledge among those familiar with the rabbinic tradition that Haman was considered a descendant of the Amalekites.
What were revelations in 1983 are common knowledge today—at least among college-bound students, parents, and counselors.
something that is generally known
It is common knowledge that that dictionary is not being updated.