[Solved] Why does this Flask code fail to add the Referrer-Policy header?@app.after_request def add_header(): response.headers['Referrer-Policy'] = 'no-referrer' return response | Flask

Flask - Security Best Practices

Why does this Flask code fail to add the Referrer-Policy header?

@app.after_request
def add_header():
    response.headers['Referrer-Policy'] = 'no-referrer'
    return response

Aafter_request cannot modify headers

BReferrer-Policy is not a valid header

CThe function is missing the response parameter

DHeaders must be set in before_request

Step-by-Step Solution

Solution:

Step 1: Check function signature
after_request functions must accept the response parameter to modify it.
Step 2: Identify missing parameter
The function lacks the response argument, so 'response' is undefined.
Final Answer:
The function is missing the response parameter -> Option C
Quick Check:
after_request needs response parameter to modify headers [OK]

Quick Trick: after_request functions must accept response argument [OK]

Common Mistakes:

MISTAKES

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Why does this Flask code fail to add the Referrer-Policy header?