IdentityServer3 2.4.x, 2.5.x, and 2.6.x before 2.6.1 has XSS in an Angular expression on the authorize response page, which might allow remote attackers to obtain sensitive information about the IdentityServer authorization response.

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.

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