Continuing the discussion from Linkify words in post, theme component:
The click track / topic link extraction code has had more than its fair share of bugs in the past, and it’s past due to come up with a mitigation so that the next of these bugs to come up doesn’t completely break people’s experience.
When it can’t identify the link in the post, show a page that lets people (1) still visit links even if something’s messing with the click tracking system and (2) also prevents the forum from being used as an open redirect.
An apologetic interstitial, with the forum branding (layout: no_ember) and in a style reminiscent of Chrome’s SSL error pages, should be fine.
At a code level, the problem is the conflation of the two conditions here. If
redirect=false is specified, the link was opened in a new tab and this was fetched in the background. But if
@redirect_url is blank, the code couldn’t verify the link and should really show an error message instead of absolutely nothing.