Fix XSS from cookie tossing #10431
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Fix XSS from cookie tossing #10431
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[ReleasePrep][2025.04.28]RI of dev into main
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Every time NuGetGallery receives a HTTP request it looks for a cookie named
__Controller::TempDataand loads key-value pairs from itscontent into
WebViewPage.TempDatadictionary. The value of theTempData["RawErrorMessage"]is is injected into HTML as is without any encoding inHeader.cshtml- basically in all pages.The cookie is untrusted input and can be set for example from related subdomain.
See https://www.usenix.org/system/files/conference/usenixsecurity15/sec15-paper-zheng.pdf and https://media.blackhat.com/eu-13/briefings/Lundeen/bh-eu-13-deputies-still-confused-lundeen-slides.pdf for more information.
For example, a XSS vulnerability in a subdomain of https://nuget.org (or any other deployment of NuGetGallery) would enable an attacker to create a
__Controller::TempData"shadow" cookie in a victim's, NuGetGallery administrator, browser with a/Adminpath. This cookie would supersede the genuinepath=/; HttpOnly; Securecookie when the victim opens their NuGetGallery deployment Admin area.This is not exploitable by itself as it requires another XSS in subdomain or MitM to unencrypted subdomain endpoint. However it 1. allows for persistence (the cookie is reloaded and injected for every page visit) 2. Doesn't require the browser user to be logged into NugetGallery to inject XSS payload into the shadow cookie when visiting the vulnerable subdomain.