The Symfony blog pas posted something they're calling the Symfony 500 + 100 Challenge, an effort to kickstart some backlog cleanup of the number of issues currently in the project's backlog.

The end of the year is approaching, and we think that this is the best time to do some backlog cleaning before fresh starting the new year. Right now there are 728 pending issues in symfony/symfony repository and 177 issues in symfony/symfony-docs.

Some of those issues were reported a long time ago and they probably refer to Symfony versions that are no longer maintained. Others would have been fixed but not closed and there could also be some duplicates. That's why we ask your help to review all the pending issues in order to close irrelevant issues and achieve much more manageable levels: 500 issues or less for symfony/symfony and 100 issues or less for symfony/symfony-docs.

If you're interested in helping out, they've included a few steps to get you started locating and claiming an issue for you to work on. They also make suggestions on how to report back issues found on bugs, feature requests and general discussion items.