The Electroneum codebase includes code inherited from Monero which will break the entire network at block 202612 (about 40 days from now.)
On September 4, 2014, somebody exploited a flaw in the Monero code to cause block #202612 to evaluate to an incorrect hash. He jammed 514 transactions into the block in order to do this (an insanely high number for Monero.) See MRL-0002 for more details on this.
The attacker caused the network to fork into two separate chains as part of his attack, and in doing so, caused widespread issues across the Monero network. No coins were double-spent or counterfeited during this time.
As a result of the attack, Monero hardcoded a fix into the codebase to force the client to see the wrong hash as correct. This kept block 202612 valid, and fixed the issue.
The Electroneum code, because it was forked from Monero, carelessly includes this unnecessary fix. Even worse, once block 202612 is mined, due to the inclusion of this code, the entire network will break down. All clients will think that the hash of block 202612 is incorrect, and will refuse to accept it and any subsequent blocks. Basically, if the Electroneum network does not soft-fork to fix this within 40 days, it will be taken out by this issue.
UPDATE!!!!
https://www.reddit.com/r/Electroneum/comments/7tmd96/electroneum_update_facebook_post/dtdkcm7/
I personally am a fan of how they responded to the FUD.
I'm not. I disclosed and helped patch the bug, yet they accused me of having "vile behaviour and a disgusting lack of respect". They also accused me of spreading "negative speculation and misinformation being pushed out regarding Monero Block 202162". They accused me of putting out "distorted data", when the code that would destroy the network was literally right there in get_block_longhash, no ifs, ands, or buts.
This is an open-source community. Disclosure of issues should be applauded and thanked, not attacked. It is outrageous that the Electroneum team has decided to attack me for helping them.