Obligatory response that you're not relying solely on your own ability to examine code for problems, but the entire universe of those able to do so.
With proprietary code, you're restricted to audits done by those whom the code author has allowed to do so (or who have surreptitiously obtained the source ... and having done so, put themselves at legal risk by disclosing their findings).
With proprietary code, you're restricted to audits done by those whom the code author has allowed to do so (or who have surreptitiously obtained the source ... and having done so, put themselves at legal risk by disclosing their findings).