Currently, AbuseFilter extension provides a custom log page at Special:AbuseLog which does not currently display "Show IP" links for temporary accounts that caused a log entry.
To address that, T388124: CheckUser IP reveal: Support IP reveal on Special:AbuseLog aims to re-enable the "Show IP" button after fixing it to show the IP associated with the specific AbuseFilter log.
This task is to implement the backend changes for that task, that is, a new endpoint to be used by CheckUser's IP Reveal that accepts AbuseFilter log IDs.