Back in 3.3 we had CONF-19257 but it seems not to be fixed correctly until 5.5 because still the "last-edited" doesn't respect the global setting for NOT displaying (custom) userprofiles correctly and still tries to display the profiile pictures, that causes invalid images / broken images

1. Set global permissions for anonymous user to not allow displaying user profiles: (the setting in the lower right)
2. create a page with the last-updated macro with settings
   • social
   • show user profiles
3. assure that the "stream" will contain at least one user edit / action with a custom userprofile / image
4. display page as login'ed user,
   works great
5. open page in an anonymous tab / new browser / log out (with cleared cache!!)
   Images are not displayed because they are restricted (that's ok so far) BUT
   anonymous picture should be shown instead
   In Internet Explorer, this bug is obvisious because a red-crossed image placeholder is shown. For Chrome only a blank image is shown

Have a look at my test-page on https://wiki.childno.de/x/SgCDAQ where I created that case.

Blogpost / Stream seems to work fine.