Experts said the excessive use of Active X also made South Korean computer users more vulnerable to malware and viruses as it facilitated downloading and installing programs on the Internet without caution.
The state-run Korea Internet Security Agency said among 200 major South Korean websites, 74 percent used Active X as of July and its use was especially high among financial companies and online book sellers.
Some voters welcomed Ahn's pledge to end the mandatory, government-designated online certificate system, as many believed it had limited their choice of web browsers and computer operating system, as well as slowing down their computers.
"I think it is a well-made pledge," said Yu Kyu-yeol, a 30-year-old web developer. "I use Mac computer and every time to make payments online I had to turn on my Windows computer."
A former medical doctor and entrepreneur, Ahn is one of the three leading candidates for Dec. 19 presidential election.
Youkyung Lee can be reached via Twitter: www.twitter.com/YKLeeAP