While no users were affected, at least according to Apple, the so-called Spectre vulnerability can involve attacks on Safari in relation to chip-design security flaws that date back for decades. Read all about the updates to address this here:

https://www.usatoday.com/story/tech/talkingtech/2018/01/08/mac-and-iphone-users-listen-up-apple-issues-updates-protect-safari-attacks/1014017001/