The CheckUser extension does not store the IP address associated with the log event for a page creation. This is because the log entry is deliberately never published to Special:RecentChanges as shown in PageUpdater::doCreate.

This means that no IP address data is logged for this log event and as such when a user with the ability to reveal temporary account IPs tries to reveal the IP for this log action there will be no data. Instead the data will be associated with the revision ID that created the page and instead this should be used for this log action type.

Found by @GMikesell-WMF as part of QA on T355434.

Steps to replicate the issue

1. Enable temporary account autocreation
2. Create a new page using a temporary account
3. Log into an account with the checkuser group
4. Go to Special:Log
5. Click on Show IP next to the temporary account username on the log event for the creation of the page

What happens?:
The data is unavailable and no IP address is displayed

What should have happened instead?:
The IP address used to make the first revision of the page should be displayed.

Software version

MediaWiki 1.42.0-alpha (570bd68) 13:28, 6 February 2024. CheckUser 2.5 (9fafdf8) 11:03, 13 February 2024