> ... targets with specific profiles of interest to the Candiru customers received ads that carried JavaScript or other code that connected to Candiru’s control servers. In response, those servers delivered an exploit that served the zero-click payload when the ad appeared on an individual’s device.

> The research doesn’t describe the vulnerabilities exploited in the zero-click attacks or the final malware that was installed in them. It’s likely they were zero-days that have been fixed after Citizen Lab discovered the campaign. Citizen Lab didn’t immediately respond to questions.

Sounds like your realistic countermeasures are ad blockers, and default-disabling js.