When Active Exploitation Hits: What January's KEV Update Reveals About Browser Risk

In mid-January, CISA updated its Known Exploited Vulnerabilities (KEV) catalog with actively exploited browser vulnerabilities. Federal agencies received remediation deadlines. For everyone else, KEV additions signal that attackers are already using these exploits and defenders need to respond. 

The challenge appears after the decision to patch. Remediation requires impact analysis, testing, change approvals, and coordinated deployment. When exploitation is confirmed and active, that time window creates the highest operational risk. 

The shift to in-session attacks 

Browser exploits increasingly execute inside the session itself. GhostFrame, a recent phishing framework, uses dynamic browser-executed content that adapts per session, including iframe-based techniques.  

Traditional defenses inspect content before it reaches the browser. In-session attacks execute after inspection completes, inside environments where admin credentials, cloud consoles, and sensitive workflows are already active. This shifts where controls need to operate. 

Operational constraints during remediation windows 

KEV-driven urgency encounters predictable constraints: 

• Change control and stability requirements slow patch deployment in production environments
• Dependency chains across apps, identity systems, and endpoint tooling extend remediation timelines
• Third-party and managed platforms limit what internal teams can change directly
• Critical workflows continue during elevated risk periods: admin portals, SaaS dashboards, cloud management interfaces, investigative browsing 

Browser-based access to these systems remains necessary while remediation proceeds. 

Why detection needs to be paired with containment 

Logging and alerting remain foundational for detecting anomalies, understanding scope, and supporting incident response. During active exploitation windows, security teams also need controls that reduce exposure during ongoing operations. 

Browser sessions during this period often include: 

• Untrusted web content executing in the same environment as trusted administrative work
• Sessions handling credentials, tokens, and privileged actions
• User interactions required for business operations 

The operational question becomes: what reduces the likelihood that a compromised session leads to broader breach while remediation completes? 

Controls that address the remediation gap 

Effective compensating controls during this period share a common characteristic: they limit what can execute and where sensitive data persists during high-risk workflows. 

Security teams implementing these controls focus on specific outcomes:

• Containing execution so untrusted content does not run directly on endpoints
• Reducing data persistence on local devices for administrative and sensitive browsing sessions
• Constraining exfiltration paths from sessions handling regulated information
• Maintaining operational continuity for critical workflows during heightened threat periods 

Session-level containment addresses these requirements. Users interact with necessary content while execution occurs in isolated environments, reducing reliance on endpoint security posture during elevated-risk periods. 

These controls operate during remediation, not as a replacement for it. 

Questions for January’s KEV response 

Organizations responding to January’s KEV update can use these questions to translate urgency into actionable priorities:

1. Which browser workflows remain active during remediation windows? Identify sessions that continue during elevated risk: admin portals, cloud consoles, investigative browsing.
2. Where does sensitive data exist during those sessions? Review clipboard activity, downloads, uploads, tokens, cached data, and local persistence patterns.
3. What controls reduce exposure without halting operations? Evaluate measures that constrain execution and limit data persistence during high-risk workflows.
4. How are dynamic, in-session threats being addressed? Phishing frameworks that adapt per user session  valuate measures that constrain execution and limit data persistence during high-risk workflows.

• KEV additions create a timing challenge. The period between confirmed exploitation and complete remediation represents the highest operational risk window.
• Browser sessions serve as primary access paths during this period. Administrative interfaces and SaaS consoles remain operational when threat levels increase.
• In-session attack techniques like GhostFrame execute after static inspection completes, requiring controls that operate during session execution.
• Compensating controls during remediation gaps should address where untrusted code executes and how sensitive data persists or exits the session.
• Session-layer containment can reduce endpoint trust dependencies during remediation periods without requiring workflow interruption.

Planning for predictable gaps

The remediation gap between vulnerability disclosure and complete deployment is a known operational reality. Organizations can incorporate session-level containment by using secure environments for high-risk browsing and administrative workflows as a standard control during these periods, alongside patching schedules, monitoring infrastructure, and incident response procedures.