{"id":"CVE-2026-55876","state":"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.","publishedAt":"2026-10-15T17:23:07.781Z","updatedAt":"2026-10-21T01:01:03.086Z","severity":{"score":3.5,"label":"Low","version":"3.1","vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:N/I:L/A:N","source":"GitHub_M"},"assigner":"GitHub_M","products":["HeliumEdu platform"],"affected":[{"vendor":"HeliumEdu","product":"platform","versions":[{"version":"< 2.2.60","status":"affected"}]}],"references":["https://github.com/HeliumEdu/platform/security/advisories/GHSA-7r65-76fw-ch5c","https://github.com/HeliumEdu/platform/commit/f0de5c985c701942758b805a3d11dfb008a6af88"],"weaknesses":["CWE-79"],"ingestedAt":"2026-10-29T20:12:24.861Z","source":{"repository":"CVEProject/cvelistV5","path":"cves/2026/55xxx/CVE-2026-55876.json","commit":"556c9d3a8cd17e218bb8e452ba7cd619a384ff47"},"raw":{"dataType":"CVE_RECORD","dataVersion":"5.2","cveMetadata":{"cveId":"CVE-2026-55876","state":"PUBLISHED","datePublished":"2026-10-15T17:23:07.781Z","dateUpdated":"2026-10-21T01:01:03.086Z","assignerShortName":"GitHub_M","assignerOrgId":"a0819718-46f1-4df5-94e2-005712e83aaa","dateReserved":"2026-06-17T16:59:42.759Z"},"containers":{"cna":{"title":"Helium: Stored XSS via Unrestricted SVG File Upload — Authenticated Users Can Store Executable Scripts","descriptions":[{"lang":"en","value":"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."}],"affected":[{"vendor":"HeliumEdu","product":"platform","versions":[{"version":"< 2.2.60","status":"affected"}]}],"references":[{"url":"https://github.com/HeliumEdu/platform/security/advisories/GHSA-7r65-76fw-ch5c","name":"https://github.com/HeliumEdu/platform/security/advisories/GHSA-7r65-76fw-ch5c","tags":["x_refsource_CONFIRM"]},{"url":"https://github.com/HeliumEdu/platform/commit/f0de5c985c701942758b805a3d11dfb008a6af88","name":"https://github.com/HeliumEdu/platform/commit/f0de5c985c701942758b805a3d11dfb008a6af88","tags":["x_refsource_MISC"]}],"metrics":[{"cvssV3_1":{"attackComplexity":"LOW","attackVector":"NETWORK","availabilityImpact":"NONE","baseScore":3.5,"baseSeverity":"LOW","confidentialityImpact":"NONE","integrityImpact":"LOW","privilegesRequired":"LOW","scope":"UNCHANGED","userInteraction":"REQUIRED","vectorString":"CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:U/C:N/I:L/A:N","version":"3.1"}}],"problemTypes":[{"descriptions":[{"cweId":"CWE-79","lang":"en","description":"CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')","type":"CWE"}]}],"providerMetadata":{"shortName":"GitHub_M","orgId":"a0819718-46f1-4df5-94e2-005712e83aaa","dateUpdated":"2026-10-15T17:23:07.781Z"},"source":{"advisory":"GHSA-7r65-76fw-ch5c","discovery":"UNKNOWN"}},"adp":[{"title":"CISA ADP Vulnrichment","references":[{"url":"https://github.com/HeliumEdu/platform/security/advisories/GHSA-7r65-76fw-ch5c","tags":["exploit"]}],"metrics":[{"other":{"type":"ssvc","content":{"timestamp":"2026-10-21T01:00:34.594595Z","id":"CVE-2026-55876","options":[{"Exploitation":"poc"},{"Automatable":"no"},{"Technical Impact":"partial"}],"role":"CISA Coordinator","version":"2.0.3"}}}],"providerMetadata":{"shortName":"CISA-ADP","orgId":"134c704f-9b21-4f2e-91b3-4a467353bcc0","dateUpdated":"2026-10-21T01:01:03.086Z"}}]}}}