In http-proxy-middleware before 2.0.8 and 3.x before 3.0.4, writeBody can be called twice because "else if" is not used.
{
"versions": [
{
"introduced": "0"
},
{
"fixed": "2.0.8"
},
{
"introduced": "3.0.0"
},
{
"fixed": "3.0.4"
}
]
}