To reproduce, go to the piwik demo, select a widget, and click on export anywhere.
We contacted clearspring a while ago but no answer see forum post
We have a few possible solutions:
1 - remove this feature from Piwik
2 - find another provider like clearspring providing similar API
3 - contact clearpspring and ask them again why this is happening, and if we can somehow secure a user id
4 - ask users to provide their own clearspring user ID in order to use the feature
If we can't do 3- or 4- quickly we should just do 1- and remove clearspring feature from Piwik.
Removed clearspring support. It only worked well for a few months before they eventually banned us or something... Probably not a good idea to have Piwik relying on a 3rd party tool anyway.