More browsers = More exploits. An attacker may not know which browser you use, but the linked site could contain multiple exploits to cover more than one browse

More browsers = More exploits. An attacker may not know which browser you use, but the linked site could contain multiple exploits to cover more than one browser. Also, this exploit didn't even escape the IOS sandbox. Instead it was exfiltrating active logins to social networking / email sites. The weakness is that attackers were able to violate the same-origin policy and that allowed them to read those cookies from a malicious site. It says that these attackers are mitigated by 'site-isolation' which is in chrome and firefox. Hopefully Safari will add similar capabilities soon.