I don’t believe that Open Source == Less Secure. See also: Linux, Ngix, Postgres... Many many open source projects are secure. They’re not perfect but an argument could be made that they’re more secure BECAUSE they’re open.

Software with crosshairs on its back practicing garbage security practices will be pwnd the same regardless of it’s open-ness.

Honestly. With a lot of the tools out there these days. I question if it’s even faster to hunt security bugs by reading the source rather than just attempting common exploits via tooling.