Containers are not a magic shield that protects you from all attacks. You should still be wary of what you're running even with the additional protection they offer.
For example - https://seclists.org/oss-sec/2019/q1/119
For example - https://seclists.org/oss-sec/2019/q1/119
Nor are manual reviews by Apple staff...
https://cve.mitre.org/cgi-bin/cvename.cgi?name=CVE-2017-1087