issue2551098: markdown links missing rel="noreferer nofollow" Links generated by all markdown backends are missing the noopener and nofollow relation that roundup's normal text -> html core adds to prevent security issues and link spam. Now rel="nofollow" is added to links generated by markdown2 backends and rel="nofollow noopener" for mistune and markdown backends. Markdown2 isn't as programable as the other two backends so I used the built-in nofollow support. This means that a user that generates a link that opens in a new window can manpulate the parent window.

def audit_html_files(db, cl, nodeid, newvalues):
    if 'type' in newvalues and newvalues['type'] == 'text/html':
        newvalues['type'] = 'text/plain'
    

def init(db):
    db.file.audit('set', audit_html_files)
    db.file.audit('create', audit_html_files)