CSP Headers not being sent/received by ZAP Browser

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kodeeo

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Sep 26, 2025, 6:32:24 AM (11 days ago) Sep 26
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I am sure my website is sending out CSP headers, but when I analyze it trough ZAP, it always complains the CSP header is not set. 

Upon checking from the ZAP browser, the header does not in fact get sent. 

But if I use my normal browser (mozilla firefox, the very same installation ZAP uses) the header does get sent. 

What is happening and why? My application does not have any user-agent specific rule about sending CSP


kingthorin+zap

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Sep 26, 2025, 10:13:18 AM (11 days ago) Sep 26
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You probably have a Replacer rule or script that's removing it.

Michele Romanin

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Sep 26, 2025, 10:18:17 AM (11 days ago) Sep 26
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Is something like this enabled by default?
I am pretty sure I am running ZAP with default settings, I've not made any script or replace rule

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kingthorin+zap

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Sep 26, 2025, 11:10:28 AM (11 days ago) Sep 26
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Nope
Are you using HUD?

Michele Romanin

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Sep 26, 2025, 11:11:54 AM (11 days ago) Sep 26
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I have disabled it, and also I have disabled the flag in the settings to strip CSP for the HUD

kingthorin+zap

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Sep 26, 2025, 11:38:25 AM (11 days ago) Sep 26
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I can't think of anything else, but it's hard to debug when not in front of it.

Simon Bennetts

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Sep 30, 2025, 4:37:50 AM (8 days ago) Sep 30
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You should be able to confirm if ZAP is reporting the right headers by double checking with another tool like curl.

Cheers,

Simon
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