Mattermost allows an attacker to request a preview of an existing message when creating a new message via the createPost API call, disclosing the contents of the linked message.
{
"versions": [
{
"introduced": "0"
},
{
"fixed": "7.1.6"
},
{
"introduced": "0"
},
{
"last_affected": "7.7.1"
},
{
"introduced": "0"
},
{
"last_affected": "7.8.0"
}
]
}