Out of nowhere, I started getting the error when I try to post any article. After in-depth investigation, I found if I add any code snippet, I cannot save or publish the article due to getting 403 Forbidden error in the server.
Other articles are suggesting to do following things:
- Disable all plugins
- Fix folder/file permission
- Re-generate .htaccess file
I have tried all of it, but I was not able to fix the issue.
After few struggling, I realised that my code snippet in the post is blocked by Mod Security, not because of WordPress 5 upgrade or plugins.
In the VentraIP, they are providing Mod Security (Web Application Firewall) by default. And it is pretty sophisticated tool to protect the website. Read more: https://www.modsecurity.org/about.html
So I have simply created e-ticket in VentraIP to ask customer service to whitelist the rule that blocking the code snippet. As usual, VentraIP customer service is awesome. They whitelisted and now 403 Forbidden is gone.
It may not be great tip, but as the person I struggled to find out what it is, hope it helps some people having same issue.