[Dosenpfand]

Please stop spreading FUD.

>In the meantime, users of the reference implementation do not need to be concerned. Transactions are always tracked properly by the Bitcoin-Qt/bitcoind software.

https://bitcoinfoundation.org/blog/?p=418

[mason55]

Interesting. This thread on reddit states that it IS an issue in the reference implementation and includes a patch

http://www.reddit.com/r/Bitcoin/comments/1xm49o/due_to_activ...

Edit: The concern with the Bitstamp appears to be confusion due to transaction malleability and NOT actual double spend or cancellation issues. However the BTC reference client is not perfect at handling malleability and only gets it right eventually.

[makomk]

While it's not an issue if you're using the GUI, the official client makes it hard for API consumers to track what's going on. As far as they're concerned, the transaction they requested never succeeds and a new one with a completely different ID that they never sent appears. It's entirely up to API consumers to reliably match the new, different transaction up with what they originally requested - and the API doesn't actually expose the information they need to do this cleanly.