[1]https://arstechnica.com/information-technology/2021/12/hackers-drain-31-milli
on-from-cryptocurrency-service-monox-finance/?amp=1

   Blockchain startup MonoX Finance said on Wednesday that a hacker stole
   $31 million by exploiting a bug in software the service uses to draft
   smart contracts.

   The company uses a decentralized finance protocol known as MonoX that
   lets users trade digital currency tokens without some of the
   requirements of traditional exchanges. “Project owners can list their
   tokens without the burden of capital requirements and focus on using
   funds for building the project instead of providing liquidity,” MonoX
   company representatives [2]say here. “It works by grouping deposited
   tokens into a virtual pair with vCASH, to offer a single token pool
   design.”

   IFRAME: [3]amp_iframe0

   An accounting error built into the company’s software let an attacker
   inflate the price of the MONO token and to then use it to cash out all
   the other deposited tokens, MonoX Finance [4]revealed in a post. The
   haul amounted to $31 million worth of tokens on the Ethereum or Polygon
   blockchains, both of which are supported by the MonoX protocol.

   Specifically, the hack used the same token as both the tokenIn and
   tokenOut, which are methods for exchanging the value of one token for
   another. MonoX updates prices after each swap by calculating new prices
   for both tokens. When the swap is completed, the price of tokenIn—that
   is, the token sent by the user—decreases and the price of tokenOut—or
   the token received by the user—increases.

References

   1. https://arstechnica.com/information-technology/2021/12/hackers-drain-31-million-from-cryptocurrency-service-monox-finance/?amp=1
   2. http://go.redirectingat.com/?id=100098X1555750&xs=1&url=https://medium.com/monoswap/monox-spotlight-coinlist-seed-5a45ca1e5205&sref=rss
   3. https://player.cnevids.com/interlude/arstechnica/iframe/?pageURL=https://arstechnica.com/information-technology/2021/12/hackers-drain-31-million-from-cryptocurrency-service-monox-finance/&pageType=amp-article&tags=cryptocurrency,defi,hacking,information-technology#amp=1
   4. http://go.redirectingat.com/?id=100098X1555750&xs=1&url=https://medium.com/monoswap/exploit-post-mortem-33921a779b43&sref=rss