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

Quick assessment

Affected
HeliumEdu platform
Exploitation
No confirmed in-the-wild exploitation; assess based on exposure
Recommended action
Check the vendor advisory and references for a fixed version. If immediate upgrade is impossible, restrict exposure and increase monitoring.

Helium 是一款免费的在线学生计划工具，用于管理课程、作业、成绩和笔记。在版本 2.2.60 之前， 的 POST 端点允许经过身份验证的用户上传 SVG 和 HTML 格式的附件。这是因为 文件未将这些格式列入 和 的黑名单中，而 中的附件序列化逻辑依赖于这些黑名单进行过滤。 当攻击者上传一个 为 的 SVG 文件，并且其他用户访问该附件公开的链接时，嵌入在 SVG 中的脚本将被执行。这导致攻击者能够在由应用程序管理的存储 URL 下持久化地注入和控制活动内容的，并可能发起网络钓鱼攻击。 尽管附件存储使用了与

CVSS 3.5 · Low

Possible ATT&CK Techniques 1 AI

T1505.003 · Web Shell

Affected Version Matrix 1

VendorProduct Version RangeStatus
HeliumEdu platform < 2.2.60 affected
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I. Basic Information for CVE-2026-55876

Vulnerability Information
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Vulnerability Title
Helium: Stored XSS via Unrestricted SVG File Upload — Authenticated Users Can Store Executable Scripts
Source: CVE Program / CVE List V5
Vulnerability 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.
Source: CVE Program / CVE List V5
CVSS Information
CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:N/I:L/A:N
Source: CVE Program / CVE List V5
Vulnerability Type
在Web页面生成时对输入的转义处理不恰当(跨站脚本)
Source: CVE Program / CVE List V5

Affected Products

Vendor Product Affected Versions CPE Subscribe
HeliumEdu platform < 2.2.60 -

II. Public POCs for CVE-2026-55876

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III. Intelligence Information for CVE-2026-55876

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Patches & Fixes for CVE-2026-55876 (1)

Vendor Advisories for CVE-2026-55876 (1)

IV. Related Vulnerabilities

Same product: platform
Same vendor: HeliumEdu
Same weakness: CWE-79

V. Comments for CVE-2026-55876

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