Incomplete blacklist vulnerability in mainfile.php in PHP-Nuke 7.9 and earlier allows remote attackers to conduct SQL injection attacks via (1) "/**/UNION " or (2) " UNION/**/" sequences, which are not rejected by the protection mechanism, as demonstrated by a SQL injection via the eid parameter in a search action in the Encyclopedia module in modules.php.
https://www.exploit-db.com/exploits/2617
https://exchange.xforce.ibmcloud.com/vulnerabilities/29705
http://www.vupen.com/english/advisories/2006/4149
http://www.neosecurityteam.net/index.php?action=advisories&id=27