agentsteal has reported some vulnerabilities in FirstClass, which can be exploited by malicious people to conduct cross-site scripting attacks.
1) A vulnerability is caused due to an error within the handling of "%00" sequences. This can be exploited to execute arbitrary HTML and script code in a user's browser session in context of an affected site via specially crafted URLs.
Successful exploitation may require that the victim uses Internet Explorer.
2) Input passed to the "plugin" parameter of the search functionality is not properly sanitised before being returned to a user. This can be exploited by malicious people to execute HTML and script code in a user's browser session in context of an affected site.
Vulnerability #1 is reported in versions 8.0 and 8.3. Other versions may also be affected.
Solution: Filter malicious character and character sequences using a proxy or firewall.
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