Mattermost versions 9.9.x <= 9.9.0, 9.5.x <= 9.5.6, 9.7.x <= 9.7.5, 9.8.x <= 9.8.1 fail to disallow the modification of local users when syncing users in shared channels. which allows a malicious remote to overwrite an existing local user.
{
"versions": [
{
"introduced": "9.5.0"
},
{
"fixed": "9.5.7"
},
{
"introduced": "9.7.0"
},
{
"fixed": "9.7.6"
},
{
"introduced": "9.8.0"
},
{
"fixed": "9.8.2"
},
{
"introduced": "0"
},
{
"last_affected": "9.9.0"
}
]
}