Preface In early February 2015, I reported an XSS vulnerability in HackerOne itself. After some investigation, we determined that the vulnerability was due to a bug in version 3.2.2 of the Redcarpet markdown parser … which was due to a bug in the autolink feature in version 1.16.0 of the Sundown markdown parser that Redcarpet was based off of. In short, text like this: _danlec_@danlec.com … isn't