Hospital Incident Response Checklist for a Malicious Browser Extension

How do you identify and scope the affected devices and browser profiles?

Open an incident record, appoint an incident lead, and establish a shared timeline before making changes that could erase evidence. Treat the extension as a potential entry point: determine whether it accessed browser data, credentials, or hospital applications, and whether activity reached other devices or accounts.

• Identify affected workstations, shared clinical devices, users, departments, locations, operating systems, and browsers. Prioritize systems used to access electronic health records (EHRs), patient portals, and administrative applications.
• For each browser profile, record the extension’s name, browser extension ID, version, installation source, first observed time, permissions, and whether it is enabled. Use the ID rather than the display name to search across managed-browser and endpoint records. Google’s Chrome Enterprise guidance on extension policies explains how to identify extension IDs and apply controls to specific extensions.
• Review endpoint detection, browser-management, identity-provider, DNS, proxy, firewall, and EHR audit data for related activity. Search for connections to a suspected command-and-control destination and for the same extension or indicators on other endpoints.
• Determine whether browser sync was enabled, which data types could sync, and whether the extension appears in other profiles or devices associated with affected users. A browser sync policy may help establish where to look and whether sync controls should be temporarily changed; Microsoft documents that its Edge sync policy can exclude extension data from synchronization.
• Keep the scope provisional until you have checked potentially affected profiles, endpoints, accounts, and connected services. Update it as new evidence emerges.

For Microsoft Edge’s sync policy documentation, extension data is one of the data types administrators can exclude from sync. Verify the applicable controls for each browser in use rather than assuming one vendor’s settings apply to another.

How should the hospital contain affected systems and block malicious activity?

Choose containment actions that reduce the threat without unnecessarily interrupting patient care or destroying evidence. Coordinate the plan with the incident lead, clinical operations, and the teams responsible for affected systems.

• Use endpoint management or browser administration to disable or block the identified extension ID across managed devices and profiles. If the incident is active, restrict suspicious outbound connections and block known malicious domains or destinations at the appropriate network controls, while retaining relevant logs.
• Quarantine affected endpoints or place them on a restricted remediation network when feasible. If immediate isolation could disrupt care, work with clinical leadership to preserve essential EHR and medical-device connectivity while limiting other access.
• Consider temporarily restricting extension synchronization or other relevant sync functions if evidence suggests they are spreading the extension. Apply changes through approved management controls and verify that they take effect.
• Preserve evidence before wiping or rebuilding a device when circumstances permit. Document the action, its time, the person who authorized it, the expected operational impact, and any exception made to protect care delivery.
• Reassess containment as the investigation develops. A block on one endpoint or one destination may not contain activity on other profiles, systems, or accounts.

CISA’s incident response playbook recommends considering service availability and evidence preservation when evaluating containment, alongside isolating affected systems and blocking unauthorized activity. Its playbook is federal guidance, so apply it in conjunction with the hospital’s incident response and clinical downtime procedures.

How do you remove the extension and check for persistence?

After evidence is preserved and containment is in place, remove or disable the extension across every affected browser profile. Removing it from one user’s profile does not establish that it is gone from other devices or that the device itself is clean.

• Use centrally managed browser controls to block the extension and prevent reinstallation. Confirm the policy has reached affected devices and profiles; do not rely only on a user manually selecting “Remove.”
• Inspect browser-management settings, forced-install lists, extension update sources, and other configuration changes. Look specifically for a rogue browser update policy or unauthorized extension-management policy that could reinstall the extension or redirect its updates.
• Check for operating-system persistence, including unexpected startup entries, scheduled tasks, services, scripts, or newly installed applications. Compare changes with approved software and configuration baselines.
• Review registered native messaging host entries, their manifests, referenced executables, and modification times. A browser may communicate with a registered native application through this mechanism; Chrome’s native messaging documentation describes how hosts are registered and how extensions can communicate with them.
• Check whether the extension or related settings return after browser restart, policy refresh, or user sign-in. If the device has unexplained persistence or its integrity cannot be established, follow hospital policy for a clean rebuild or reimage.
• Before restoring the browser to service, apply trusted browser and operating-system updates, confirm approved policies, and monitor for the extension ID and related indicators.

Use the recovery process to address the underlying cause—not just the visible extension. NIST SP 800-61 Rev. 3 recommends identifying affected hosts and services, looking for persistence, and verifying restored assets before returning them to normal operation.

How should you protect accounts and assess exposure of patient information?

Assess what the extension could access and what the available evidence shows it actually accessed. An extension’s presence alone does not prove that patient information was viewed or disclosed; limited or missing telemetry also does not prove that no access occurred.

• Compare the extension’s permissions and behavior with browser, identity, EHR, proxy, DNS, and endpoint records. Look for unusual sign-ins, access to patient records, searches, downloads, exports, or outbound transfers during the exposure window.
• Identify which users signed in to hospital applications from affected profiles and which authentication material may have been exposed. Where compromise is suspected, perform session token revocation, terminate active sessions, rotate affected credentials or secrets, and review multifactor authentication methods in line with the identity team’s procedures.
• Ask the EHR and application owners to preserve and analyze audit logs, including the records and actions associated with affected user accounts. Record what the logs can establish, what they cannot establish, and any gaps in retention or visibility.
• Have the privacy officer and legal counsel assess whether protected health information (PHI) was impermissibly accessed or disclosed and whether the information was unsecured. Document the basis for the determination.

Under the HIPAA Breach Notification Rule, an impermissible use or disclosure is generally presumed to be a breach unless the covered entity or business associate demonstrates a low probability that PHI was compromised through a documented risk assessment. HHS identifies four factors: the nature and extent of the PHI, who received or used it, whether it was actually acquired or viewed, and how the risk was mitigated. See HHS’s Breach Notification Rule guidance. A malicious extension incident is not, by itself, a final breach determination.

What evidence should you preserve during investigation and remediation?

Preserve the evidence needed to understand the incident, determine scope, assess exposure, and support recovery. Capture relevant data before removal, reimaging, or other changes that could overwrite it, when doing so is safe and consistent with hospital procedures.

• Record device identifiers, affected user and browser profile, browser version, extension ID and version, installation source, permissions, relevant policy settings, and the observed timeline.
• Preserve available extension files and manifests, browser profile and policy data, browser or management-console records, endpoint telemetry, and relevant operating-system logs.
• Export identity-provider, EHR audit, DNS, proxy, firewall, and network records for the relevant period. Include records of connections to suspected command-and-control destinations and any blocking actions taken.
• Document every collection and response action: who performed it, when, what was collected or changed, how it was acquired, and where it is stored. Preserve original copies where possible and restrict access to incident records.
• Follow the hospital’s evidence-retention and handling procedures. If litigation, law-enforcement referral, or other formal proceedings are possible, involve legal counsel and follow applicable chain-of-custody requirements.

NIST SP 800-61 Rev. 3 recommends recording investigative actions and preserving the integrity and provenance of incident data and metadata. It also notes that incident response records may contain sensitive information and should be safeguarded.

How should incident response teams coordinate clinical operations and notifications?

Use a single response structure to coordinate technical work, clinical continuity, privacy decisions, and communications. Set a reporting cadence so operational leaders can make timely decisions without requiring every responder to contact separate stakeholders.

• Include information security, endpoint and network teams, clinical operations, EHR administrators, privacy, legal, compliance, communications, and relevant vendors. Involve executive leadership when an action could materially affect critical services.
• Agree on which services must remain available, which affected devices can be isolated, and how staff should use approved downtime procedures if normal access is disrupted. Provide staff with clear, verified instructions for reporting issues and avoiding suspected browser prompts or extensions.
• Maintain an incident status record that distinguishes confirmed findings, working hypotheses, unresolved questions, and decisions. Share only the information needed by each stakeholder and protect sensitive incident details.
• Have the privacy officer and counsel determine whether notification is required under HIPAA, state law, contracts, or other applicable requirements. If a breach of unsecured PHI is determined, HIPAA requires notice to affected individuals without unreasonable delay and no later than 60 days after discovery; HHS and media notification rules depend on the number affected and other circumstances.
• Coordinate any notice to patients, regulators, business associates, law enforcement, or the public through the designated officials and established procedures. Document the decision, applicable deadlines, and supporting assessment.

HHS’s notification guidance describes the applicable HIPAA requirements, while NIST SP 800-61 Rev. 3 recommends coordinating response activities with appropriate internal and external stakeholders and following applicable notification requirements.

What controls can prevent another malicious browser extension incident?

Reduce opportunities for unapproved extensions to reach clinical and administrative systems, and make policy changes visible to security teams. Test controls with clinical users and application owners before broad deployment so prevention does not block essential workflows.

• Use an extension allowlist or an equivalent managed-browser configuration that permits only reviewed, necessary extensions. Block unapproved extensions by default where supported, and define an exception process with a named owner and review date.
• Review extension permissions, publisher, update source, and access to sensitive sites before approval. Reassess approved extensions when permissions, ownership, or update behavior changes.
• Apply and validate browser-management policies across supported browsers and devices. Google’s Chrome Enterprise policy guidance describes settings for allowing, blocking, or managing extensions and checking that policies have applied.
• Manage browser sync deliberately. Where appropriate, restrict extension synchronization for hospital profiles and monitor policy changes or unexpected sync behavior.
• Alert on new extension IDs, unexpected extension changes, unauthorized update sources, unfamiliar native messaging hosts, and suspicious browser traffic. Retain browser, identity, endpoint, and EHR audit records long enough to support investigations.
• Provide staff with a simple way to report unexpected extensions, browser warnings, or redirected pages. Test incident response and clinical downtime procedures together, then update controls based on lessons learned.

A resilient response combines accurate scoping, careful containment, evidence preservation, account protection, clinical coordination, and preventive browser controls. Review the incident record and recovery results to verify that affected systems are clean, patient-care workflows are functioning, and the cause has been addressed.

FAQs

Should an affected hospital device be disconnected from the network immediately?

Not automatically. If the device is actively sending data or endangering other systems, rapid isolation may be appropriate. But first consider patient-care impact, evidence preservation, and whether a restricted remediation network or narrower network block can contain the threat while preserving essential clinical access. Follow the hospital’s incident command and downtime procedures.

How can teams determine whether patient information was accessed?

Correlate the extension’s permissions and observed behavior with EHR audit logs, identity sign-ins, endpoint telemetry, and network records. Check for record views, searches, exports, downloads, and outbound transfers during the exposure window. Have the privacy officer and legal counsel assess the findings under the applicable breach rules; absence of a relevant log entry is not proof that access did not occur.

What browser records should be preserved during the investigation?

Preserve the extension ID, version, manifest and permissions, browser profile and policy data, installation source and timing, available browser-management records, and relevant endpoint logs. Also retain identity, EHR audit, DNS, proxy, and firewall data, plus a record of each investigative action and evidence transfer. Follow the hospital’s retention and handling procedures.

How can hospitals prevent unauthorized browser extensions from being installed?

Manage browsers centrally, block unapproved extensions by default where practical, and use an extension allowlist for reviewed tools. Validate that policies apply across devices and profiles, control extension sync where appropriate, monitor for new IDs and policy changes, and provide a documented exception and reporting process.