CVE-2026-78207 - exceljs through 4.4.0 Prototype Pollution via deepMerge Reached From Note Serialization

CVE-2026-78207 - exceljs through 4.4.0 Prototype Pollution via deepMerge Reached From Note Serialization

https://cvefeed.io/rssfeed/latest.atom / Mon, 08/24/2026 - 04:28
CVE ID :CVE-2026-78207
Published : Aug. 24, 2026, 1:16 a.m. | 1 hour, 10 minutes ago
Description :exceljs-hardened before 5.0.0 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.
Severity: 9.4 | CRITICAL
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