Added http-litespeed-sourcecode-download:

http-litespeed-sourcecode-download.nse exploits a null-byte poisoning vulnerability in Litespeed Web Servers 4.0.x before 4.0.15 to retrieve the target script's source code by sending a HTTP request with a null byte followed by a .txt file extension (CVE-2010-2333).

If the server is not vulnerable it returns an error 400. If index.php is not found, you may try /phpinfo.php which is also shipped with LiteSpeed Web Server. The attack payload looks like this:
* <code>/index.php\00.txt</code>

References:
* http://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2010-2333
* http://www.exploit-db.com/exploits/13850/

scripts/script.db

@@ -79,6 +79,7 @@ Entry { filename = "http-form-brute.nse", categories = { "auth", "intrusive", }
 Entry { filename = "http-google-malware.nse", categories = { "discovery", "external", "malware", "safe", } }
 Entry { filename = "http-headers.nse", categories = { "discovery", "safe", } }
 Entry { filename = "http-iis-webdav-vuln.nse", categories = { "intrusive", "vuln", } }
+Entry { filename = "http-litespeed-sourcecode-download.nse", categories = { "exploit", "intrusive", "vuln", } }
 Entry { filename = "http-majordomo2-dir-traversal.nse", categories = { "exploit", "intrusive", "vuln", } }
 Entry { filename = "http-malware-host.nse", categories = { "malware", "safe", } }
 Entry { filename = "http-methods.nse", categories = { "default", "safe", } }