Assume breach.

In other words, you shouldn't use vulnerability counts, but you can discern patterns of vulnerability to intuit something about the nature of the codebase.

For example, RCE vulnerabilities on Chrome, especially under V8 while not very common they happen commonly enough to suspect that maybe there is some code quality issue. However, if you look at the sheer size of V8, and how much scrutiny and research it undergoes, it is surprising there aren't even more critical vulns being found all the time. JIT is inherently a risky endeavor.