My problem appears to be a reintroduction of the previously resolved bug CONF-5848.

I verified that it worked correctly in 2.3.3, we just noticed it this week after upgrading to 2.9.1.

{blog-posts:labels=foo}

results in all news being shown if the label foo is not attached to any news items.

I did find that if I used match-labels=all as in the following:

{blog-posts:labels=foo|match-labels=all}

No news items were found, which is the correct behavior.

Dean