[Solved] You wrote this code to add a security header but it does not appear in responses:@app.after_request def add_header(response): response.headers.... | Flask

Flask - Security Best Practices

You wrote this code to add a security header but it does not appear in responses:

@app.after_request
def add_header(response):
    response.headers.add('X-Content-Type-Options', 'nosniff')
    return response

What is the issue?

AYou must call response.commit() to save headers

BThe header name is incorrect

CThe function should be named 'before_request'

DThe method 'add' does not exist on response.headers; use assignment instead

Step-by-Step Solution

Solution:

Step 1: Check response.headers API
response.headers is a dictionary-like object; it does not have an 'add' method.
Step 2: Correct way to set header
Use assignment: response.headers['X-Content-Type-Options'] = 'nosniff'.
Final Answer:
The method 'add' does not exist on response.headers; use assignment instead -> Option D
Quick Check:
Set headers by assignment, not add() method [OK]

Quick Trick: Use response.headers['key'] = 'value', not add() [OK]

Common Mistakes:

MISTAKES

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