Please explain for those of us who are not good enough in the field (I'm genuinely asking). I was under the impression that software like GnuPG and OpenSSL cou

Please explain for those of us who are not good enough in the field (I'm genuinely asking). I was under the impression that software like GnuPG and OpenSSL could be considered safe, so seeing a security professional warning about a negative track record of open source cryptography is worrisome. What exactly should we be careful of when it comes to open source cryptography?