the filter assignment is not maintained correctly.
If a filter is assigned to a feed the feed id is stored in the field feeds in table filters.
All ids of the feeds this filter is assigned to are stored in this field in a comma separated list.
if you delete a feed a filter is assigned to and afterwards add a new feed
the new added feed gets the id of the just deleted feed.
Now the filter will be applied to this new feed because the feed id was not removed from the comma separated list in the field feeds in table filters during deletion.
This should be improved!