When I am trying to upload a file via wordpress I get
The file you are uploading was rejected by the server.
It probably contents viruses or trojans that can damage your website
Do not attempt to upload it again as your IP address may be blocked.
Found the answer. it was because of plugin Pyxsoft Anti Malware & Security. Needed to login into WHM => Plugins => Pyxsoft Anti Malware => HTTP Inspector Tab => Enable http upload inspector - set to No.