- Plesk for Linux
- Debian 9 (Stretch) or Ubuntu 18.04 is used;
- ModSecurity Rules by Atomicorp are missing in Plesk at Tools & Settings > Web Application Firewall (ModSecurity)
This is Plesk bug with ID PPPM-10946. It is fixed in Plesk Obsidian 18.0.21, which is going to be released in November, 2019.
At the moment, there is no workaround available.
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