Mattermost versions 9.5.x <= 9.5.5 and 9.8.0, when using shared channels with multiple remote servers connected, fail to check that the remote server A requesting the server B to update the profile picture of a user is the remote that actually has the user as a local one . This allows a malicious remote A to change the profile images of users that belong to another remote server C that is connected to the server A.
{
"versions": [
{
"introduced": "9.5.0"
},
{
"fixed": "9.5.6"
},
{
"introduced": "0"
},
{
"last_affected": "9.8.0"
}
]
}