This assumes a mature XP process is underway (this is almost 20 years old, so should not be a surprise to anyone).
If you are actively developing software there are only a limited category of bugs:
- The critical – stop development and fix
- The important – to be picked up as the next highest priority item
- Prioritised alongside other upcoming work items.
- Do not fix – record as unimportant
These days there should be no reason to keep an extensive bug backlog.
A bug is effectively a missing test (unit, integration or end-to-end).
With a sufficient test suit the QA should be getting bored. Hopefully they are spending the time working on acceptance criteria and acceptance tests for upcoming work.