Every Friday at noon Pacific (3pm New York, 9pm Berlin, 6am Saturday in Sydney) I will be in #drupal-contribute helping people fix critical issues. I will prepare 2-3 issues with up to date, actionable issue summaries, familiarize myself with the problems and the suggested solution in the issue so that I can answer questions.
If you're someone who has already worked some in the Drupal.org issue queue (so are familiar with patches, coding standards, etc.), even if your experience is not in the core queue, please come by! It's helpful if you know something of Drupal 8 as well, but not necessary.
If you're new to contributing to Drupal in general, you can go to https://www.drupal.org/core-mentoring for a session or two to learn the skills you need to fix critical issues. If you're new to Drupal 8, https://api.drupal.org/api/drupal/8 is a great starting point.
Hope to see you there!