GHSA-Q22Q-2RRF-M27P Mattermost allows unsolicited invites to expose access to local channels

Mattermost versions 9.9.x = 9.9.0, 9.5.x = 9.5.6, 9.7.x = 9.7.5 and 9.8.x = 9.8.1 fail to disallow unsolicited invites to expose access to local channels, when shared channels are enabled, which allows a malicious remote to send an invite with the ID of an existing local channel, and that local...