A fix for what? XC wasn't attacked. Anyway, in case your post was true and not a FUD attempt, below is the response from Dan.
In response to the attack that was carried out today on navajocoin.
While I am still reviewing the limited amount of information, based on my review of both the code and the available data, the attack was successful partly due to the 30 second block time.
XC use's a 90 second block time.
I am reviewing the additional variables & Proof of Stake code involved in this attacked for any potential issues
Thank you for Dan citation, so we know this is most recent info on that subject today. Waiting for Dan's final conclusion and/or solution coming soon...