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Set content type to `application/json` for `flask.make_response` with JSON data


ImportanceReview GuidanceRequires Scanning Tool
MediumMerge Without ReviewNo

The default mimetype for make_response in Flask is 'text/html'. This is true even when the response contains JSON data. If the JSON contains (unsanitized) user-supplied input, a malicious user may supply HTML code which leaves the application vulnerable to cross-site scripting (XSS). This fix explicitly sets the response type to application/json when the response body is JSON data to avoid this vulnerability. Our changes look something like this:

from flask import make_response, Flask
import json

app = Flask(__name__)

def foo(request):
json_response = json.dumps({ "user_input": request.GET.get("input") })
- return make_response(json_response)
+ return make_response(json_response, {'Content-Type':'application/json'})

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Why is this codemod marked as Merge Without Review?

This change will only restrict the response type and will not alter the response data itself. Thus we deem it safe.

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