Steps to reproduce:

1. create a new blog post, and restrict it to yourself
2. log in as another user and go to Blogs in sidebar
3. blog is not visible in the blogs summary page
4. click a visible blog in the same month
5. click the month link in the breadcrumb
5. restricted blog (title and excerpt) is visible in the month summary page

If you go to the month summary page from the sidebar, the restricted blog is not visible. Only seems to happen via the breadcrumb.