In this case shit software. For a secure conference software there should be no possibility for the user to accept invalid certificates.
The developer always has to plan with what we call a DAU in germany (Dümmster anzunehmender User = dumbest user possible), and even that user should have no possibility to accidentally share a secure conference. So as a developer I would: Lock the user to certificates and encryption keys I deem secure and hook into the low level OS functions to grab the screen and disable them to prevent accidental sharing via software like Anydesk and the like which the user forgot to close. This would even interrupt the functions of a simple trojan on the PC.
Of course a dedicated attacker with physical or admin access to the device could always break these. But then you have another big security breach.