>An acute diplomatic crisis broke out between the United States and Sweden in 2006 when Swedish authorities put a stop to CIA rendition flights [...]

> Steven V. Noble wrote in cables reveled by WkiLeaks that the Swedish government reacted strongly because rules had not been followed.

> A spokesperson from Säpo, Swedish police Intelligence Service, confirmed parts the newspaper report, adding that there have been no more extraordinary rendition flights landing in Sweden since.

I have not found any references to subsequent rendition flights involving Sweden, and it's been a good while since that article was published.

Apart from that, I don't really know what kind of confirmation you can be asking for. One cannot conclusively rule out the possibility that Sweden is still involved in extraordinary rendition, but one also cannot rule out that possibility for the UK, or for many other countries that Assange has spent time in.