ExpressionEngine before 5.4.2 and 6.x before 6.0.3 allows PHP Code Injection by certain authenticated users who can leverage Translate::save() to write to an _lang.php file under the system/user/language directory.
{
"versions": [
{
"introduced": "0"
},
{
"fixed": "5.4.2"
},
{
"introduced": "6.0.0"
},
{
"fixed": "6.0.3"
}
]
}