NXMH, a Belgian investment company owned by NXC, acquired the majority of Bitstamp shares in October 2018. NXC also owns the South Korean cryptocurrency exchange Korbit and the Korean-Japanese video game company Nexon.
The majority stake, approximately 80%, is now held by NXC and the purchase price is estimated at approximately $400 million. CEO Kodrič retains a 10% stake in Bitstamp, while Pantera Capital's remaining shares amount to 7%.

Company Background

Bitstamp was established in Slovenia in July 2011 but later relocated its registration to the UK in April 2013 and to Luxembourg in 2016.
It is the second largest Bitcoin exchange in Europe, right behind Kraken Bitcoin Exchange.

picture taken by Marco Verch, CC BY 2.0

Infobox - Comparison of crypto exchanges

Rank	Exchange	Markets	Volume (24h) 5th Nov 2018
#01	OKex	514	$775M
#25	Kraken	69	$90M
#32	Bitstamp	14	$60M
#63	Korbit	8	$12M

Sources and additional links:

https://coinmarketcap.com/rankings/exchanges/
https://cryptocoincharts.info/markets/info
https://www.reuters.com/article/us-bitcoin-exchange-bitstamp/european-investment-firm-buys-digital-exchange-bitstamp-in-all-cash-deal-idUSKCN1N314I
https://bitcoinexchangeguide.com/bitstamp-crypto-exchange-ownership-change-looks-to-be-just-the-start-of-management-shakeups/
https://www.bitdegree.org/tutorials/bitstamp-vs-kraken/#The_Bitstamp_Story