Anyone saying that is definitely wrong, it is neither more secure or less secure just on the basis that it is closed or open source. There are processes that all types of software must take to ensure there are limited vulnerabilities. Security audits, pen testing, code scanning, etc.

There is some security to obscurity, but I'd argue that the more prevalent a system is the more having visible source adds security. When it comes to unscrupulous behavior by vendors - like those who would embed backdoors in communications element - shining light on the farm corners of their code definitely provides some security.

At the very least, if the company that supplies a product goes under, there's a better possibility of getting a new vendor to support or patch it if they can actually get their hands on the source.

It's in a radio standard that's used in Europe, and the backdoor apparently exists in multiple radios from different vendors which use the standard. Here is direct link to the article, which seems to work for me https://www.wired.com/...

Might be related, Archive.today has this strange configuration where you can't connect to their sites if you use a DNS server that don't send EDNS Client Subnet (e.g. cloudflare dns 1.1.1.1).