If you gloss over the Safari release notes – like the Safari 26.2 release notes – you see a lot of trailing “(12345678)”-mentions in the list of fixed bugs. These numbers are the internal bug IDs, as used within Apple’s internal bug tracker fka “Radar” (now Feedback Assistant).
These numbers are not linked to anything because Radar is an Apple-internal tool, so to external people these numbers are practically useless … or are they?