HERITAGE FINANCIAL CORP /WA/

Item 8.01 Other Events On or about March 2, 2026, Heritage Financial Corporation (the “Company”) detected a cybersecurity incident involving an internal file share server used by employees and the exfiltration of files from that file share server which may contain personal information. The Bank’s customer accounts, customer systems and operations were not impacted. Promptly following detection, the Company initiated its security incident response plan and began deploying measures to stop the unauthorized activity, including taking the affected system offline. The incident did not cause any disruptions in the Company’s operations, which have continued throughout this time in the ordinary course. The Company has launched a thorough investigation and engaged experienced external advisors, including an independent forensic investigation firm and legal counsel, to assess, contain, and remediate the incident. The Company also promptly notified its banking regulators, law enforcement and cyber insurance carrier. While the investigation is ongoing, as of the date of this filing, the Company has not determined that the cyber incident is material or that it has had, or is reasonably likely to have, a material impact on the Company’s financial condition or results of operations. Forward-Looking Statements Statements made in this Form 8-K that look forward in time or that express management’s beliefs, expectations, or hopes are forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995, as amended. Such forward-looking statements reflect the views of management at the time such statements are made. These statements include, but are not limited to, those regarding actions being taken and that will be taken in response to the cyber incident,