There are entirely too many secret societies within the Catholic church.the Catholic Church Is ONE, it is Holy, it is Catholic and it is Apostalic, does not include secret societies.
Opus Dei isn’t a “secret society”. Anyone can come to an OD retreat or other function. The only thing that’s “secret” about it is that those who are active in it aren’t supposed to flaunt it; St. Josemaria wanted Opus Dei to be a vehicle to make people better Catholics, not “Opus Dei members”.
This has started because of Dan Brown Novels because of being best sellers. Which then went into popular culture. He used made up material with a somewhat legitimate title of an organization. Also his movie versions.