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.
{
"cpes": [
"cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:*",
"cpe:2.3:a:mattermost:mattermost_server:7.7.1:*:*:*:*:*:*:*",
"cpe:2.3:a:mattermost:mattermost_server:7.8.0:*:*:*:*:*:*:*"
],
"severity": "Medium"
}