FireEye documented more than 1,500 vulnerabilities affecting ICS disclosed in the past 15 years. The majority of the vulnerabilities documented by the experts was spotted after 2010, the year that cyber security expert link to the discovery of the cyber weapon Stuxnet. The 2015 is considered the Annus horribilis for the ICSs, the experts observed a spike due to 92 security issues disclosed by two vendors. 33 percent of the flaws were zero-day vulnerabilities, and more than 100 were unpatched when they were publicly disclosed.”]
Source: http://securityaffairs.co/wordpress/50026/security/ics-flaws-report.html