Cape codes older than 2016 can still be redeemed

Minecon cape codes, older than 2016 can still be redeemed by decoding it with Base64. Making the blocking of 2015, 2013, 2012 Minecon cape codes absolutely useless. They're blocked because of sellers (? - source).

Update: It actually seems like the decoder isn't on the site, see WEB-1287. Still, this might be Mojang's way of blocking these codes but its not very good then.

How to

Use base64decode to decode the cape code but remove the == or %3D part (depends on year).