OpenSea Warns of Phishing Attacks Due to Data Breach

A third-party vendor’s employee misused their access to OpenSea’s customer data, the head of security said

article-image

Blockworks Exclusive Art by Axel Rangel

share
  • A Customer.io employee shared email addresses with an unauthorized external party
  • OpenSea warned users of fraudsters trying to impersonate the platform by using fake domain names

Collectibles platform OpenSea has alerted customers to a data breach after staff found email addresses were shared with an external party.

Head of Security Cory Hardman said in a blog post on Wednesday that an employee of Customer.io, OpenSea’s email delivery vendor, abused their access by downloading and externally sharing customer data. 

“If you have shared your email with OpenSea in the past, you should assume you were impacted,” he wrote. “We are working with Customer.io in their ongoing investigation, and we have reported this incident to law enforcement.”

The company further warned customers might face phishing attacks — attempts by cybercriminals posing as credible institutions with an aim to obtain sensitive information — by using a domain name similar to the official “opensea.io,” such as “opensea.org” or “opensae.io.”

Screenshots posted to Twitter show OpenSea notified customers about the data breach via email. Some users demanded compensation.

Loading Tweet..

Customer.io told Blockworks that the employee in question has been suspended and had access removed, pending an internal investigation. “We are working closely with OpenSea and are reviewing exactly how these email addresses were compromised,” a spokesperson for the vendor company said.

A similar incident occurred in March, when hackers breached third-party marketing vendor HubSpot to target large crypto stakeholders. NYDIG, Pantera Capital, BlockFi, Circle and Swan Bitcoin were among the affected companies.

OpenSea found itself in a sea of trouble thanks to another incident prior the data breach. The Department of Justice earlier this month charged its former head of product, Nathaniel Chastain, with insider trading in connection to non-fungible tokens (NFTs). He was charged with one count of wire fraud and another count of money laundering.

Chastain resigned from his position at OpenSea in September after he was suspected of profiting from inside information and purchasing NFTs before they were posted publicly.

OpenSea remains the leading marketplace by volume by a wide margin, with over six times the sales of the second-largest NFT marketplace over the past 30 days, according to data from DappRadar.


Get the news in your inbox. Explore Blockworks newsletters:

Tags

Decoding crypto and the markets. Daily, with Byron Gilliam.

Upcoming Events

Marina Bay Sands Singapore

October 7, 2026

DAS Asia is a a single-day summit at Marina Bay Sands Singapore featuring conversations between the builders, investors, and global leaders are shaping the trajectory of the digital asset ecosystem in Asia & North America.

Hilton Park Lane, London

November 10-11, 2026

DAS London is a two-day summit at the Hilton Park Lane in London featuring conversations between the builders, allocators, and policy makers who are shaping the trajectory of the digital asset ecosystem in the UK, Europe, and North America.

recent research

Ethereum Purple (2).jpg

Research

EIP-8363 would progressively burn validator rewards as the staking ratio rises, reaching a 0% staking yield above a 50% staking ratio, limiting issuance-driven stake growth while preserving incentives for validators to perform their duties. Supporters argue that lower issuance would reduce unnecessary dilution, strengthen ETH’s monetary premium and maintain a large unstaked constituency capable of resisting validator capture. Critics contend that the modest inflation reduction may not justify the risks to staking products, institutional demand and the LST-based DeFi economy. Its equilibrium and prospects for adoption remain highly uncertain.

Newsletter

The Breakdown

Decoding crypto and the markets. Daily, with Byron Gilliam.

Blockworks Research

Unlock crypto's most powerful research platform.

Our research packs a punch and gives you actionable takeaways for each topic.

SubscribeGet in touch

Blockworks Inc.

133 W 19th St., New York, NY 10011

Blockworks Network

PodcastsNewslettersEventsRoundtablesAnalytics