The Confluence search box used to say "Search this space" if the Documentation theme option is set to restrict the search to the current space.
It now says just "Search". This implies that Confluence will search the full site, which is misleading. It also discourages people from using the search, when they specifically want a restricted search. See this topic on Atlassian Answers:
I don't see a search box (at the top looks like global search, over all versions, so I don't want that because I would have to go through the slow navigation back to my version again.