Yesterday, an order to sell 8 bitcoin (BTC), worth $60,000, tanked the price of Bitcoin on a single trading pair on crypto exchange Binance. It was either a fat-fingered mistake or there were more nefarious plans underway.

The trade was made on the trading pair between bitcoin and a stablecoin—a cryptocurrency that keeps its price pegged to a fiat currency, like the US dollar—called StableUSD (USDS).

With a 24-hour trade volume of just over $130,000, the large sell order represented more than half of this trading pair's daily trade volume, allowing it to sell through the order book and crash Bitcoin to a low of $681.81—on this trading pair—before recovering. Despite the flash crash, bitcoin is currently trading at a price of $7,393, up 1.6% for the day.

StableUSD was launched a year ago by Stably. However, its maket cap has been cut in half since its first few months, showing that fewer people are making use of the stablecoin. It is now ranked 542 on CoinMarketCap. In contrast, stablecoins like Tether have seen their market caps rise drastically, over this time.

This isn't the first time a sudden move like this has happened on this trading pair before. In April, when the price of bitcoin was $5,000, it jumped up to $11,000 on this trading pair, also on Binance.

There are three main reasons why somebody would sell a huge amount of bitcoin at a below-market rate. The first of these is that somebody simply made a mistake and placed a limit sell order for far below market rate. If this is the case, then at least one buyer got incredibly lucky and managed to purchase a massive amount of bitcoin for under $700.

The next two options involve manipulating the market in order to profit.

One explanation is that traders might be doing this to manipulate the market, for example, by simultaneously crashing the market and shorting it—betting against its future price. Margin or leverage trading could be used to increase the effect of doing so. However, this is unlikely in this case because there are no futures trading offerings for this trading pair, making it hard to profit from the endeavor.

Alternatively, coins are sometimes sold below market value in order to transfer money from one account to another. If a hacker takes control of someone else's account—for example via phishing techniques—they might be unable to withdraw directly from the compromised account and will often use this kind of tactic. However, this also seems fairly unlikely in this case, since the amount was so high.

Either way, BTC:USDS is the lowest volume stablecoin trading pair on Binance, so—unless this changes—it will stay particularly vulnerable to manipulation. And if the stablecoin's usage continues to drop, it may disappear anyway.