This article is a part of our Vulnerability Database (back to index)
Cross-site Scripting occurrences in Identityserver4
** DISPUTED ** IdentityServer IdentityServer4 through 2.4 has stored XSS via the httpContext to the host/Extensions/RequestLoggerMiddleware.cs LogForErrorContext method, which can be triggered by viewing a log. NOTE: the software maintainer disputes that this is a vulnerability because the request logger is not part of IdentityServer but only our development test host. (2019-05-21, CVE-2019-12250)
IdentityServer IdentityServer4 1.x before 1.5.3 and 2.x before 2.1.3 does not encode the redirect URI on the authorization response page, which might lead to XSS in some configurations. (2018-03-22, CVE-2018-8899)
Why Cross-site Scripting can be dangerous
Cross site scripting is an attack where a web page executes code that is injected by an adversary. It usually appears, when users input is presented. This attack can be used to impersonate a user, take over control of the session, or even steal API keys.
The attack can be executed e.g. when you application injects the request parameter directly into the HTML code of the page returned to the user:
https://server.com/confirmation?message=Transaction+Complete
what results in:
<span>Confirmation: Transaction Complete</span>
In that case the message can be modified to become a valid Javascript code, e.g.:
https://server.com/confirmation?message=<script>dangerous javascript code here</script>
and it will be executed locally by the user's browser with full access to the user's personal application/browser data:
<span>Confirmation: <script>dangerous javascript code here</script></span>