Removing the source is an easy fix, just uncheck 3CORESEC from IP Address Blocklist in the Firewall menu and click Save
(This screen shot is outdated so let me know if you need more assistance 
)
Looks like I have been recommending 3CORESEC since I started using the official IPFire blocklist, in Aug 2022,
They were a reputable source way before that and part of Emerging Threads and Suricata rules.
It is even stranger that ET removed them without any announcements and now they return 404 error
https://rules.emergingthreats.net/open/suricata-7.0.3/rules/3coresec.rules
