Cookieless browsing broken after update KB4580979
Upon running Windows Update KB4580979, .Net 4.7.2 projects that have the SessionStateSection.Cookiless Property set to AutoDetect no longer functions as expected. Previously, a browser that blocked cookies would be redirected to the same page with the querystring /default.aspx?AspxAutoDetectCookieSupport=1 and upon the system detecting that cookies were not supported it would redirect again to a cookiless session URL e.g. /(X(1)S(adl04pietheradyfawfaqlym))/default.aspx?AspxAutoDetectCookieSupport=1 Since the update, a browser would continously be redirected to /default.aspx?AspxAutoDetectCookieSupport=1 until the redirects exceeded the maximum redirects. Relevant Web.config section: <configuration> <system.web> <sessionState cookieless="AutoDetect" /> </system.web> </configuration> Windows Server 2019 DataCenter Version 1809 OS Build 17763.1369