Career profile
Sean Cassidy
Chief Information Security Officer (CISO), Plaid
- Current role, per sources checked 7 September 2026
- June 2026
Sean Cassidy is the Chief Information Security Officer (CISO) of Plaid, appointed in June 2026.
Career path
Before joining Plaid, Cassidy served as Head of Security at Asana. Earlier in his career he was Head of Information Security at Patreon. Prior to that, he held the position of Chief Technology Officer at DefenseStorm. Earlier still, Cassidy worked at Praesidio, building security products as a whitehat hacker. Before Praesidio, he worked at Limelight Networks, where he built the company's video transcoding system, and at Cisco Systems, where he worked on the ASA firewall product. Cassidy holds a Master of Computer Engineering from RIT. He has been involved in the information security community for over a decade and is the author of numerous open source projects.
Public talks and writing
While at Praesidio, Cassidy was frequently invited to speak at conferences, presenting experiments, hacks, and best practices in cybersecurity. One of his presentations, delivered on March 29, 2016, was titled Role Based Behavior Analytics - Patterns and Anomalies in User Behavior as Indicators of Attack, which addressed how security teams can distinguish anomalous behavior on a company network following a run of major industry breaches. He also writes a blog about programming and startups.
Context of the appointment
Cassidy's move to Plaid was one of several CISO appointments tracked across the industry in 2026, as CSO Online reported a high rate of change in the upper ranks of corporate security that year. CSO Online's roundup of new CISO appointments for 2026 listed the move, noting that "Sean Cassidy joins Plaid as CISO." SecurityWeek's industry-moves coverage, which tracks hiring announcements, promotions, and career achievements in the cybersecurity community, carried the fuller account of his appointment and prior roles.
