Is this "transaction malleability" really an issue? The well-known Bitcoin exchange Mt.Gox last week suspended all Bitcoin withdrawals because of "technical issues", which today have been better described in this press release.

This looks like a serious problem, but is it actually true?
Has this issue been confirmed by third parties?
Has it really been known "for a while"?
What true impact can it have?
Here's a good interview by Gregory Maxwell himself who's a Bitcoin developer: 


  Oh there is a “problem” in the Bitcoin protocol, known since at least
  2011 (see the link I gave). But for normal applications, not involving
  unconfirmed transactions, it shouldn’t cause any severe problems
  because wallets can handle it locally.


This has to do with systems, such as Mt.Gox, that rely on unconfirmed transactions. Normal Bitcoin apps don't rely on unconfirmed transactions.

The Transaction Malleability issue that Mt.Gox talks about has been around since 2011. It only effects transactions which are not included in a block. Once a block is hashed, you can't change the transactions within it because then the hash of the block would have to change as well.

For all other Bitcoin applications that rely on confirmed transactions, as they should, this is not an issue.