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Content-Length being added even when disabled

Robert | Last updated: Apr 08, 2020 08:41PM UTC

Using the match/replace in proxy no matter what I do I keep getting Content-Length added for example Content-Length: 1122 even when I create response find/replace for Content-Length: \d+ /aaaaaaaaaaaaaaa I just end up with 2 Content-Length. I guess Match and replace needs a "Automatically update Content-Length head with Match and Replace" HTTP/1.1 100 Continue Content-Length: 1122 HTTP/1.1 200 OK Date: Wed, 08 Apr 2020 20:34:14 GMT Content-Type: application/json; charset=utf-8 Connection: close X-Powered-By: Express Access-Control-Allow-Origin: * Vary: X-HTTP-Method-Override, Accept-Encoding ETag: W/"296-UCcQM+Imv05+/PjDjS9ESui+97A" CF-Cache-Status: DYNAMIC Expect-CT: max-age=604800, report-uri="https://report-uri.cloudflare.com/cdn-cgi/beacon/expect-ct" Server: cloudflare CF-RAY: 580ec4994dfff1ba-ATL aaaaaaaaaaaaaaa

Robert | Last updated: Apr 08, 2020 08:44PM UTC

I'm guessing burp is thinking that the header is just "HTTP/1.1 100 Continue" and its adding the Content-Length: even tho that's not the end of the header because it's out of spec basically?

Uthman, PortSwigger Agent | Last updated: Apr 09, 2020 08:41AM UTC

Hi, Is your intention to remove the Content-Length header entirely? If so, can you tell me the settings you have configured under Match and Replace in Proxy > Options?

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