Security certificate errors in Zotero
Note: These instructions are only for use with security software that intercepts/scans HTTPS connections, a WebDAV server with a self-signed certificate, or an institutional network that monitors encrypted traffic using a custom root certificate authority (CA). You should never override certificate errors unless you understand the consequences. When in doubt please contact your network administrator or ISP.
Zotero does not currently provide a graphical way to whitelist self-signed certificates or custom root certificates, so you will need to copy files from a working Firefox installation.
If you use a WebDAV server with a self-signed certificate, you can open the WebDAV URL in Firefox, accept the certificate, and then copy the cert_override.txt file from the Firefox profile directory to the Zotero profile directory.
If you or your organization is using a custom certificate authority, which can be the case when using security software or connecting via a proxy server, it may be necessary to use Firefox 52 ESR and copy the cert8.db file as well. (Later versions of Firefox will produce a cert9.db file that won't work in the current version of Zotero. An upcoming release will support the newer format.)