Ann: Mesoblast Type A Meeting with FDA, page-469

While they might be malicious, short attacks aren't wholly illegal.

However, there can be illegal attempts to drive a stock's price down below its true asset value. This includes market manipulation in the form of bribing people to avoid a company's offering or producing slander about a company to keep it from being profitable. If a fund is charged with an act of interference like this, they won't be charged with a "short attack" per se, but rather manipulating the market in a monopolistic way (which would result in an antitrust trial in the US).

IN the US, the SEC does hold restrictions on abusive short sales that operate in this fashion.

Or there can be a coordinated effort to downramp a stock, especially at crucial or vulnerable times, to shake out retail investors or those who don't have a deeper understanding of the stock.
As here. Participants are operating in a grey area of the law and they invariably know it. The carpet has been worn out on the way to the legal counsel's office for some...