For some time, the Slackware security mailing list is not functioning as it used to be, and news about lack of Security updates are also discussed on LWN. People may have forgotten that Slackware also have a changelog that provides all the information you need about any updates to Slackware.
Well, that kind of problem is now being fixed as i received bunch of security update posts that happened in the last batch of updates. Let's hope there will be no more problem like this in the future and negative news about Slackware will be gone.
Meanwhile, i suggest you to keep a good look on Slackware's changelog rather than relying on the list itself.