Changelog
A dated, numbered list of what changed in a product, kept by whoever ships it — the shortest answer to whether a fix is actually out.
It is a primary source, and that is its whole value. A release note carries a version number and a date; a post that retells it usually carries neither, so a claim like „the bug is fixed“ has nothing to be checked against. When a changelog and an announcement disagree, the changelog wins: an announcement is written before shipping, a changelog after it.
Three things are worth reading in every entry. What broke, listed as breaking changes. What is going away, listed as deprecations. And whether the version is released or only being rolled out to part of the users — that last one explains most of the confusion, because a version can sit in the changelog for days before it reaches your account.
For a site like this one the changelog is also the fastest verification step. A version number turns a story into something a reader can check in half a minute; its absence turns the same story into a claim.