Why was the Oct 2015 Transaction Malleability event possible in spite of BIP62/66? The recent re-emergence of transaction malleability has been responsible for a large number of Txs which are being double spent (October 2015).

/r/Bitcoin has posted some C++ code which @amaclin has taken responsibility for. 

I understand that, based on this source code, the transaction malleability "exploit" is simply tweaking the DER signatures for certain Txs (ie non P2SH Txs) and rebroadcasting the Tx (disclaimer: I don't know C++ so these are educated guesses). 

BIP62 deals with numerous issues, amongst these is the requirement for canonical DER signatures: I was under the impression canonical DER signatures was implemented in BIP66. 


Can someone clarify what @amaclin's code is doing?
Why is this exploit possible if BIP66 was implemented several weeks ago?
Canonical DER signature implemented in BIP 66 fixes issue #1 of BIP 62 ( Non-DER encoded ECDSA signatures ) 

Amacilin's code exploits issue #5 in BIP 62 ( Inherent ECSDA signature malleability ),  and is explained here : https://github.com/bitcoin/bitcoin/commit/a81cd96805ce6b65cca3a40ebbd3b2eb428abb7b 

This issue was fixed by requiring signatures to have low-S encoding in pull request 6769 : https://github.com/bitcoin/bitcoin/pull/6769 . Note that this fix only prevents mutated transactions from being relayed (transactions without low-S encoding can still be mined into blocks).