Highlighting the main issue here (from the article):

“This means that it is possible for the WhatsApp server to add new members to a group,” Martin R. Albrecht, a researcher at King’s College in London, wrote in an email. “A correct client—like the official clients—will display this change but will not prevent it. Thus, any group chat that does not verify who has been added to the chat can potentially have their messages read.”

Unless their company has enterprise m365 accounts and copilot is part of the plan.

Or if they’re running a local model.