Server variable value duplicated when IIS Default Document module invoked?

[Wight, Jared]

The following issue has been reproduced in Shibboleth SP 3.2.2 and 3.2.3 (can't reproduce in 3.2.1) running on Windows Server with IIS. This behavior was first observed on a 2012 R2 server running IIS 8.5. It has been reproduced on new Server 2019 servers running IIS 10. The issue appears to have been introduced in v3.2.2.

Is anyone else seeing this behavior?

[/secure/default.aspx]
<% @ Page Language="C#" %>
<%
Response.Write("Request[\"displayName\"]: " + Request["displayName"] + "<br>");
%>

Visiting the path below (which loads default.aspx via the IIS default document module) results in the attribute value appearing twice in the server variable (separated by a semicolon):
https://<domain<https://%3cdomain> name>/secure/
Request["displayName"]: Rick Sanchez;Rick Sanchez

Visiting default.aspx directly results in the expected value returned in the server variable:
https://<domain<https://%3cdomain> name>/secure/default.aspx
Request["displayName"]: Rick Sanchez
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