Zoom has patched flaw that could have allowed attackers to guess a meeting ID and enter a meeting. Zoom’s conference meetings not requiring a meeting password by default, which is a password assigned to Zoom attendees for what is called a meeting room. Zoom now has added passwords by default to any scheduled meetings. Zoom will also no longer automatically indicate if meeting ID is valid or invalid when a page loads instead, the page will merely load and attempt to join the meeting. This is not the first time that vulnerabilities have been discovered in conferencing systems.
Source: https://threatpost.com/zoom-fixed-flaw-opening-meetings-to-hackers/152266/