MIT Researchers found basic rookie mistakes, when giving their time for free. Iota cryptography was broken.

We emphasize that to produce a signature on a msg2, our attacks require Alice to sign an innocent-looking related message, msg1, of our choosing. This is a chosen message attack. We have not developed a known message attack.

...Madars Virza did an independent analysis to try to directly invert the hash function using algebraic techniques (which has not yet been successful, and is not included in the report).