Facebook: "You can't post this because it has a blocked link": missing.hwpub.com
After spending at least 6 hours troubleshooting, I've finally discovered why Facebook was blocking URLs to my website.
When trying to share or save a URL from my website on Facebook, I saw the error:
The content you're trying to share includes a link that our security systems detected to be unsafe:
Please remove this link to continue.
The unsafe link (http://missing.hwpub.com) was not on my website, and didn't appear to be called by any scripts.
In my case, this error was caused by a missing favicon, a graphic image that is used in the address bar, tabs, and taskbar that provides a visual reminder of the website. According to W3.org, the correct placement of the preferred code is this:
<!DOCTYPE html PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/strict.dtd">
What was really strange was that I could share some pages, but not others. I finally noticed (after a lot of research) that the pages I couldn't share didn't include a favicon. Once I added this code, I could share the page.
I'm not sure why having the favicon code is important to sharing on Facebook. As far as I understand, favicons are not required. This looks like a bug in Facebook's system.
Details and troubleshooting
Here's some more detailed information about this issue.
Screenshot of error:
Pasting "http://missing.hwpub.com?ck=ndc96uyh76&et=1" resolves to http://dsnextgen.com/?o_id=130920&domainname=missing.hwpub.com
- I wrote to Facebook (per their instructions), and didn't hear back.
- I Googled variations on "missing.hwpub.com" and "dsnextgen.com" and couldn't find anything related to Facebook.
- I found a lot of search utilities to check URLs, but I couldn't find anything wrong with my site (here's a helpful page: http://www.malwarehelp.org/freeware-open-source-commercial-website-security-tools-services-downloads.html)
- Facebook's debugger didn't provide any clues.
- I wrote to my website hosting company -- just in case there was a problem on the server -- and they wrote back to say the problem was with Facebook.
- Finally, I found this website http://wepawet.iseclab.org/view.php?hash=712d8513ca970d6959b1cbd4bc214bee&t=1374378102&type=js that included the following:
When I looked at my website, I saw that the pages I couldn't share didn't have a favicon. As soon as I added a favicon, I could share.
Hope this is helpful for others having this problem.