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Using the firefox extension tamper data (for modifing http requests that firefox makes) how do I insert a null character into a post field? I can enter normal characters, but binary characters in it are not urlencoded and are shown as is, so how do I enter the null character into a field? If you know of a firefox extension like tamper data that I can do this or a way to do this using tamper data please post.

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Would %00 work?

I used to use burp proxy - it's a standalone Java program acting as a HTTP proxy, so can be used for anything.

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I can confirm that %00 works with Tamper Data. One exception is if your form has enctype="multipart/form-data". In that case, I'm not sure how you insert a null character in the Tamper Data request. – frankadelic Aug 9 '11 at 21:08

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