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Cyber Centre Daily Advisory Digest — 2026-04-21 (1 advisories)
The Canadian Centre for Cyber Security issued an advisory regarding multiple vulnerabilities in Mozilla Firefox and Firefox ESR. Organizations are urged to update their browser deployments to Firefox 150, Firefox ESR 115.35, or Firefox ESR 140.10 to ensure protection against potential security risks.
Conf:highAnalyzed:2026-04-21reports
Authors: Canadian Centre for Cyber Security
Key Takeaways
- Mozilla has published security advisories addressing vulnerabilities in Firefox and Firefox ESR.
- Affected products include Firefox versions prior to 150, and Firefox ESR versions prior to 115.35 and 140.10.
- Administrators and users are strongly encouraged to apply the necessary updates immediately to mitigate risks.
Affected Systems
- Mozilla Firefox versions prior to 150
- Mozilla Firefox ESR versions prior to 115.35
- Mozilla Firefox ESR versions prior to 140.10
Detection Availability
- YARA Rules: No
- Sigma Rules: No
- Snort/Suricata Rules: No
- KQL Queries: No
- Splunk SPL Queries: No
- EQL Queries: No
- Other Detection Logic: No
N/A
Detection Engineering Assessment
EDR Visibility: None — This is a vulnerability patching advisory with no specific exploitation details or behavioral indicators provided. Network Visibility: None — No network indicators or exploitation traffic patterns are described in the advisory. Detection Difficulty: N/A — No threat detection details are provided; the focus is entirely on vulnerability management and patching.
Required Log Sources
- Software Inventory
- Vulnerability Management
Hunting Hypotheses
| Hypothesis | Telemetry | ATT&CK Stage | FP Risk |
|---|---|---|---|
| Identify unexpected child processes (e.g., cmd.exe, powershell.exe) spawning from the firefox.exe process, which may indicate successful exploitation of browser vulnerabilities. | Endpoint (Process Creation) | Execution | Medium |
Control Gaps
- Patch Management
False Positive Assessment
- Low
Recommendations
Immediate Mitigation
- Update Mozilla Firefox to version 150 or later.
- Update Mozilla Firefox ESR to version 115.35, 140.10, or later.
Infrastructure Hardening
- Implement automated browser update policies across the organization using MDM or Group Policy.
User Protection
- Ensure users restart their browsers to fully apply pending updates.
Security Awareness
- Educate users on the importance of keeping web browsers up to date and responding to browser update prompts.