CVE-2026-78209: Exceljs

High severity, CVSS 8.2. EPSS: 0.4% chance of exploitation in the next 30 days.

exceljs through 4.4.0 fails to neutralize leading equals, plus, minus, or at signs in cell values written to CSV output. Attackers who can influence exported cell values can inject formulas that execute when the CSV file is opened in a spreadsheet application, potentially exfiltrating data or performing other malicious actions.

Affected products

• Exceljs Exceljs: up to and including 4.4.0

Published 2026-08-24. Last modified 2026-08-31.