Bug overview description.
Adding backslashes to any search string in the “Posts” section stops tags from matching posts, yet makes pagination appear in the otherwise empty “No posts matched your search” page.

What part(s) of the site page(s) are affected?
Posts, search

What is the expected behavior?
The site returns “No posts matched your search.”

What actual behavior is given instead?
The site returns a modified “No posts matched your search” page, with added pagination at the bottom, with as many pages as would be expected if all backslashes were removed from the search string.

Time of incident (if applicable).
2017-04-07T16:48:43Z

Can you reproduce the bug every time?
I am able to reproduce this bug both on Chrome 57.0.2987.133 and on Waterfox 51.0.1, with any number of backslashes inserted anywhere in the search string.

Errors or other messages returned (if any).
N/A

no? i searched dog -\ and it works normally. if you search dog \ it doesnt return anything because there is no posts tagged as dog AND \
if you search dog\ it doesnt return any matches because there is no posts tagged as dog\

Don't add arbitrary backslashes then? They are a valid tag character, so they are treated as part of a tag. This isn't actually a bug unless it impacts a post that contains a tag that has a backslash, and that tag cannot be searched.