Ask HN: Is Short Sellers' Borrowing Interest (Against Stock) Public Information?

If it's not, how are some companies getting the data, and how accurate is that data, if it's not public information?

Context: https://www.cnbc.com/2019/04/03/hedge-funds-are-loading-up-to-bet-against-lyft.html

The story says

> Short sellers have borrowed $455 million worth of Lyft shares, or 6.61 million shares, according to IHS Markit.

How does IHS Markit know the total amount (and # of shares) of LYFT borrowed? If this is not public information, then how accurate could that number be?

Asking because Hedge Funds are notoriously secretive, so it's unlikely that they are going out of their way to tell some market data firm like IHS Markit about their short selling strategy, so if the info is not public (EX: submitted to SEC by Law?) how reliable is all this information?

If it is public, then where can I find it?