Disabling Cloudflare features on admin pages for content management systems like WordPress
To avoid getting a site offline error message when updating the admin section of your content management system, we recommend setting a Page Rule to exclude the admin section of your CMS from Cloudflare.
Please do the following on the Page Rule interface (we’ll use WordPress admin section as an example):
- Go to the Cloudflare Page Rule app.
- Input the URL for the admin section, which is in this format: example.com/wp-admin/
- Place a * before and after the URL, so it reads as example.com/wp-admin/.
- For “Cache Level”, choose “Bypass”
- For Performance, choose “Disable Performance”
- For security, choose “Disable Security”
- Save the rule
for more details please have a look
https://support.cloudflare.com/hc/en-us/articles/200169526-Disabling-Cloudflare-features-on-admin-pages-for-content-management-systems-like-WordPress