Mattermost versions 9.11.x <= 9.11.0 and 9.5.x <= 9.5.8 fail to validate that the message of the permalink post is a string, which allows an attacker to send a non-string value as the message of a permalink post and crash the frontend.
{
"cpes": [
"cpe:2.3:a:mattermost:mattermost_server:*:*:*:*:*:*:*:*",
"cpe:2.3:a:mattermost:mattermost_server:9.11.0:-:*:*:*:*:*:*",
"cpe:2.3:a:mattermost:mattermost_server:9.11.0:rc1:*:*:*:*:*:*",
"cpe:2.3:a:mattermost:mattermost_server:9.11.0:rc2:*:*:*:*:*:*",
"cpe:2.3:a:mattermost:mattermost_server:9.11.0:rc3:*:*:*:*:*:*"
],
"severity": "Medium"
}