{"id":"CVE-2026-55876","aliases":["EUVD-2026-102221","GHSA-7r65-76fw-ch5c"],"status":"published","title":"Helium: Stored XSS via Unrestricted SVG File Upload — Authenticated Users Can Store Executable Scripts","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.","severity":{"version":"3.1","score":3.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:N/I:L/A:N","level":"low","assessor":"cna","from":"cve"},"epss":{"day":"2026-11-11","score":0.00184,"percentile":0.08102,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":false},"cwes":["CWE-79"],"published":"2026-10-15T17:23:07Z","modified":"2026-10-28T02:30:40Z","products":[{"vendor":"heliumedu","product":"platform"},{"vendor":"runzero","product":"platform"}],"references":[{"url":"https://github.com/HeliumEdu/platform/security/advisories/GHSA-7r65-76fw-ch5c","tags":["x_refsource_CONFIRM","exploit","advisory"]},{"url":"https://github.com/HeliumEdu/platform/commit/f0de5c985c701942758b805a3d11dfb008a6af88","tags":["x_refsource_MISC","fix"]},{"url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/55xxx/CVE-2026-55876.json","tags":["advisory"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-55876","tags":["advisory"]}],"sources":{"cve":[{"id":"CVE-2026-55876","title":"Helium: Stored XSS via Unrestricted SVG File Upload — Authenticated Users Can Store Executable Scripts","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.","status":"published","published":"2026-10-15T17:23:07.781Z","modified":"2026-10-21T01:01:03.086Z","cvss":[{"version":"3.1","score":3.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:N/I:L/A:N","level":"low","assessor":"cna"}],"cwes":["CWE-79"],"updated_at":"2026-11-02T14:20:12.260247Z"}],"euvd":[{"id":"EUVD-2026-102221","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.","status":"published","published":"2026-10-15T17:23:07Z","modified":"2026-10-21T01:01:03Z","cvss":[{"version":"3.1","score":3.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:N/I:L/A:N","level":"low"}],"updated_at":"2026-11-02T16:59:40.989797Z"}],"nvd":[{"id":"CVE-2026-55876","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.","status":"published","published":"2026-10-15T18:17:28.307Z","modified":"2026-10-21T01:17:39.25Z","cvss":[{"version":"3.1","score":3.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:N/I:L/A:N","level":"low","assessor":"secondary"}],"cwes":["CWE-79"],"updated_at":"2026-11-02T14:12:59.751798Z"}],"osv":[{"id":"CVE-2026-55876","title":"Helium: Stored XSS via Unrestricted SVG File Upload — Authenticated Users Can Store Executable Scripts","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.","status":"published","published":"2026-10-15T17:23:07.781Z","modified":"2026-10-28T02:30:40.924070493Z","cvss":[{"version":"3.1","score":3.5,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:N/I:L/A:N","level":"low"}],"cwes":["CWE-79"],"updated_at":"2026-11-02T15:45:11.609219Z"}]}}