Due to improper type validation in attachment parsing the Socket.io js library, it is possible to overwrite the _placeholder object which allows an attacker to place references to functions at arbitrary places in the resulting query object.
{
"versions": [
{
"introduced": "0"
},
{
"fixed": "3.3.3"
},
{
"introduced": "3.4.0"
},
{
"fixed": "3.4.2"
},
{
"introduced": "4.0.0"
},
{
"fixed": "4.0.5"
},
{
"introduced": "4.1.0"
},
{
"fixed": "4.2.1"
}
]
}