Multiple cross-site scripting (XSS) vulnerabilities in InstantASP InstantForum.NET 4.1.3, 4.1.2, 4.1.1, 4.0.0, 4.1.0, and 3.4.0 allow remote attackers to inject arbitrary web script or HTML via the SessionID parameter to (1) Join.aspx or (2) Logon.aspx.