Helium is a free online student planner for classes, homework, grades, and notes. Prior to 2.2.60, the POST /planner/attachments/ endpoint allows authenticated users to upload SVG and HTML attachments because conf/configs/common.py omits those formats from BLOCKED_ATTACHMENT_EXTENSIONS and BLOCKED_ATTACHMENT_MIME_TYPES, and helium/planner/serializers/attachmentserializer.py relies on those blocklists. An uploaded SVG served as image/svg+xml can execute embedded script when a visitor opens its public attachment URL, allowing persistent attacker-controlled active content and phishing under an application-managed storage URL. The attachment storage uses a separate origin from the application, so same-origin policy prevents the script from reading application cookies or storage, and application-session compromise is not supported by the maintained deployment configuration. This issue is fixed in version 2.2.60.
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History

Thu, 15 Oct 2026 17:30:00 +0000

Type Values Removed Values Added
Description Helium is a free online student planner for classes, homework, grades, and notes. Prior to 2.2.60, the POST /planner/attachments/ endpoint allows authenticated users to upload SVG and HTML attachments because conf/configs/common.py omits those formats from BLOCKED_ATTACHMENT_EXTENSIONS and BLOCKED_ATTACHMENT_MIME_TYPES, and helium/planner/serializers/attachmentserializer.py relies on those blocklists. An uploaded SVG served as image/svg+xml can execute embedded script when a visitor opens its public attachment URL, allowing persistent attacker-controlled active content and phishing under an application-managed storage URL. The attachment storage uses a separate origin from the application, so same-origin policy prevents the script from reading application cookies or storage, and application-session compromise is not supported by the maintained deployment configuration. This issue is fixed in version 2.2.60.
Title Helium: Stored XSS via Unrestricted SVG File Upload — Authenticated Users Can Store Executable Scripts
Weaknesses CWE-79
References
Metrics cvssV3_1

{'score': 3.5, 'vector': 'CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:N/I:L/A:N'}


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cve-icon MITRE

Status: PUBLISHED

Assigner: GitHub_M

Published:

Updated: 2026-10-15T17:23:07.781Z

Reserved: 2026-06-17T16:59:42.759Z

Link: CVE-2026-55876

cve-icon Vulnrichment

No data.

cve-icon NVD

Status : Received

Published: 2026-10-15T18:17:28.307

Modified: 2026-10-15T18:17:28.307

Link: CVE-2026-55876

cve-icon Redhat

No data.

cve-icon OpenCVE Enrichment

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Weaknesses