I'm using AnchNet's services. And We've asked AnchNet when I recieved a e-mail from our BGPMon. They said their staff was configured a wrong config on router. Also they don't know 1.1.1.0/24 is used by CloudFlare&APNIC. So they used this prefix to test.
Why let people access BGP that don't even know that 1.0.0.0/8 or 1.1.1.0/24 are part of the public internet or that decide they can use random prefixes to "test" things? :-/
It is/was not uncommon either[1]. It was never a concern since it wasn't allocated. It being a concern is a very recent phenomenon.
[1] https://www.cisco.com/c/en/us/about/press/internet-protocol-...