MODX Revolution through v2.7.0-pl allows XSS via an extended user field such as Container name or Attribute name.
{
"versions": [
{
"introduced": "0"
},
{
"last_affected": "2.7.0"
},
{
"introduced": "0"
},
{
"last_affected": "2.7.0-pl"
}
]
}