CVE-2026-78207 — exceljs through 4.4.0 Prototype Pollution via deepMerge Reached From Note Serialization
exceljs through 4.4.0 contains a prototype pollution vulnerability in the deepMerge helper that fails to reject __proto__, constructor, or prototype keys when merging note objec…
Published: 2026-08-24 · CVSS: 9.3 · CVSS 4.0
exceljs through 4.4.0 contains a prototype pollution vulnerability in the deepMerge helper that fails to reject __proto__, constructor, or prototype keys when merging note objects. Attackers can assign parsed JSON with a malicious __proto__ property to cell notes, modifying Object.prototype and affecting all plain objects created in the process.
Source: CVE Program · Revision 8b16575c39f1e1810c5e863010da073d2d3285e7