We encountered this error in our Wiki too. While the error shown in MediaWiki says:
Error contacting the Parsoid/RESTBase server: (curl error: 60) SSL
peer certificate or SSH remote key was not OK
Our detection system gave us a more standard:
cURL error 60: SSL certificate problem: unable to get local issuer
certificate (see https://curl.haxx.se/libcurl/c/libcurl-errors.html)
We inspected our SSL certificates as a consequence, although there were no visible SSL errors when browsing the site.
The problem was, in our case:
- Misconfigured SSL settings: we were missing the CA (Certificate Authority) SSL Certificate next to our SSL Certificate (using DirectAdmin with a Sectigo certificate).
Adding the CA SSL Certificate key immediately solved the problem.