As mentioned deep in the comments of
JRA-7068, the RSS URL produced by queries that use the
JIRA Toolkit
Multi-issue searcher are incorrect. It appears as though all other conditions on the filter are represented in the resulting URL, but no multi-issue keys. Make a query that uses only Multi-issue keys, and the resulting RSS will be the entire database. This makes Multi-issue keys unusable with the Confluence {jiraissues} macro.
Additionally, the PermLink link is also wrong for the same reason. You'll get a filter of the entire DB if you click permlink on a filter that uses only Multi-issue keys.
The comment in JRA-7068 mentions adding "&customfield_10190=JRA-1000,JRA-2000" on the end of the URL (adjusting the custom field # for your installation). This works for both the permlink URL and the RSS URL.
I want to make sure this is tracked in its own right. There is a workaround, but I can't expect my not-always-technical PM's to hack up URLs.