Hubspot is really more of a CRM software SaaS for (inbound) marketing and sales and services. According to
this article, customer data is stored on AWS. That means that the platforms hosts customer data for multiple clients, logically separated by different account credentials.
According to Hubspot’s press release (*), an employee account was compromised, allowing the hackers to obtain data from around 30 Hubspot accounts. An account is a Client (i.e. corporation), so it’s like stating that they may have information for a wide range of customers related to 30 different companies. Furthermore, their press release stated that the focus was on crypto companies, which were their customers, and as a result, information related to these companies’ customers are likely in possession of the hackers.
Allegedly, the information they obtained access to was contact data. Hubspot is often used to send people emails, letters, and attend their service tickets so although there is no public detail of the leaded information, the probable set is going to be in the line of name, surname, email, phone, addresses and so forth, but it will depend on what each company that using Hubspot gathered. We can see what their customer records looks like here:
https://knowledge.hubspot.com/contacts/hubspots-default-contact-propertiesThere could be more delicate data gathered in service records, but there is no public statement to this regards.
As stated in the OP, the most likely use of the information is going to be targeted phishing campaigns, whereby the emails can be tailored to address a person by his full name, relate them as being a customer of a given company (that they’d impersonate), and perhaps add some extra information from the customer record to make it more convincing – all with a call to action in a brief period of time from (phishing) email reception.
(*) See:
https://ir.hubspot.com/news/hubspots-statement-regarding-march-18-2022-security-incidenthttps://www.hubspot.com/en-us/march-2022-security-incidentNote:
If anybody wants to read a very entertaining book on working at Hubspot, from a 50+ year old’s perspective, here's a reference:
Dan Lyons – Disrupted - My Misadventure in the Start-Up Bubble (2016, Hachette Books)
Edit: Allegedly, Pantera Capital is another of the corporations impacted.