mitmproxy/examples/addons/http-modify-form.py

"""Modify an HTTP form submission."""

from mitmproxy import http


def request(flow: http.HTTPFlow) -> None:
    if flow.request.urlencoded_form:
        # If there's already a form, one can just add items to the dict:
        flow.request.urlencoded_form["mitmproxy"] = "rocks"
    else:
        # One can also just pass new form data.
        # This sets the proper content type and overrides the body.
        flow.request.urlencoded_form = [("foo", "bar")]  # type: ignore[assignment]