Wordpress error "cURL error 60: SSL certificate problem: unable to get local issuer certificate" Print

When updating WordPress (especially older versions), you may encounter the error
cURL error 60: SSL certificate problem: unable to get local issuer certificate

The cause of the problem lies in WordPress files, since this CMS uses its own root certificate store (a set of core certificates that allows verifying whether a connection is properly secure).
If this file is outdated, WordPress scripts will perceive even a perfectly safe connection as a potential fraud attempt.

To fix this, simply download the file https://raw.githubusercontent.com/WordPress/WordPress/master/wp-includes/certificates/ca-bundle.crt and upload it to the /wp-includes/certificates folder of your site, replacing the old ca-bundle.crt file there.