User blog comment:DaNASCAT/Technical Update: September 9, 2015/@comment-5558012-20150909235922/@comment-24473195-20150910092058

I wouldn't be surprised if there are some crazy emoticons on there. Some wikis simply overdo it.

That isn't really the issue. The problem was a known hack (chat hacks) used to add "gimmicks" to chat:

http://community.wikia.com/wiki/Help:Custom_chat_CSS_and_JS?oldid=983485

The fact of the matter is that the hack itself was based on a huge security exploit that was left unchecked for years. The emoticons had a similar issue.