{"id":"CVE-2026-54011","aliases":["EUVD-2026-38531","GHSA-v8qj-hxv7-mgvv","PYSEC-2026-2759"],"status":"published","title":"Open WebUI: Stored XSS in Mermaid Markdown Preview","description":"Open WebUI is a self-hosted artificial intelligence platform designed to operate entirely offline. Prior to 0.9.6,Open WebUI renders Mermaid blocks from Markdown files in the file preview panel and inserts the generated SVG into the DOM using innerHTML. Because Mermaid is configured with securityLevel: 'loose', attacker-controlled Mermaid content can be rendered unsafely in this flow. A working payload was validated through the Markdown preview path, resulting in JavaScript execution in the victim’s browser under the application origin.  This vulnerability is fixed in 0.9.6.","severity":{"version":"3.1","score":8.7,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:N","level":"high","assessor":"cna","from":"cve"},"epss":{"day":"2026-11-11","score":0.00336,"percentile":0.2731,"model":"v2026.06.15"},"facts":{"in_kev":false,"known_exploited":false,"public_exploit":false,"fix_available":true},"cwes":["CWE-79"],"published":"2026-06-17T14:14:05Z","modified":"2026-10-28T02:31:08Z","fixes":[{"ecosystem":"PyPI","package":"open-webui","fixed_in":["0.9.6"],"sources":["ghsa","osv"]}],"affected":[{"source":"ghsa","ecosystem":"PyPI","package":"open-webui","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"last_affected":"0.9.5"},{"fixed":"0.9.6"}]}]},{"source":"osv","ecosystem":"PyPI","package":"open-webui","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"0.9.6"}]}],"versions":["0.1.124","0.1.125","0.2.0","0.2.1","0.2.2","0.2.3","0.2.4","0.2.5","0.3.0","0.3.1","0.3.10","0.3.12","0.3.13","0.3.14","0.3.15","0.3.16","0.3.17","0.3.17.dev2","0.3.17.dev3","0.3.17.dev4","0.3.17.dev5","0.3.18","0.3.19","0.3.2","0.3.20","0.3.21","0.3.22","0.3.23","0.3.24","0.3.25","0.3.26","0.3.27","0.3.27.dev1","0.3.27.dev2","0.3.27.dev3","0.3.28","0.3.29","0.3.3","0.3.30","0.3.30.dev1","0.3.30.dev2","0.3.31","0.3.31.dev1","0.3.32","0.3.33","0.3.33.dev1","0.3.34","0.3.35","0.3.4","0.3.5","0.3.6","0.3.7","0.3.8","0.3.9","0.4.0","0.4.0.dev1","0.4.0.dev2","0.4.1","0.4.2","0.4.3","0.4.4","0.4.5","0.4.6","0.4.6.dev1","0.4.7","0.4.8","0.5.0","0.5.0.dev1","0.5.0.dev2","0.5.1","0.5.10","0.5.11","0.5.12","0.5.13","0.5.14","0.5.15","0.5.16","0.5.17","0.5.18","0.5.19","0.5.2","0.5.20","0.5.3","0.5.3.dev1","0.5.4","0.5.5","0.5.6","0.5.7","0.5.8","0.5.9","0.6.0","0.6.1","0.6.10","0.6.11","0.6.12","0.6.13","0.6.14","0.6.15","0.6.16","0.6.18","0.6.19","0.6.2","0.6.20","0.6.21","0.6.22","0.6.23","0.6.24","0.6.25","0.6.26","0.6.26.dev1","0.6.27","0.6.28","0.6.29","0.6.3","0.6.30","0.6.31","0.6.32","0.6.33","0.6.34","0.6.35","0.6.36","0.6.37","0.6.38","0.6.39","0.6.4","0.6.40","0.6.41","0.6.42","0.6.43","0.6.5","0.6.6","0.6.6.dev1","0.6.7","0.6.8","0.6.9","0.7.0","0.7.1","0.7.2","0.8.0","0.8.1","0.8.10","0.8.11","0.8.12","0.8.2","0.8.3","0.8.4","0.8.5","0.8.6","0.8.7","0.8.8","0.8.9","0.9.0","0.9.1","0.9.2","0.9.3","0.9.4","0.9.5"]},{"source":"osv","ecosystem":"PyPI","package":"open-webui","ranges":[{"type":"ECOSYSTEM","events":[{"introduced":"0"},{"fixed":"0.9.6"}]}],"versions":["0.1.124","0.1.125","0.2.0","0.2.1","0.2.2","0.2.3","0.2.4","0.2.5","0.3.0","0.3.1","0.3.10","0.3.12","0.3.13","0.3.14","0.3.15","0.3.16","0.3.17","0.3.17.dev2","0.3.17.dev3","0.3.17.dev4","0.3.17.dev5","0.3.18","0.3.19","0.3.2","0.3.20","0.3.21","0.3.22","0.3.23","0.3.24","0.3.25","0.3.26","0.3.27","0.3.27.dev1","0.3.27.dev2","0.3.27.dev3","0.3.28","0.3.29","0.3.3","0.3.30","0.3.30.dev1","0.3.30.dev2","0.3.31","0.3.31.dev1","0.3.32","0.3.33","0.3.33.dev1","0.3.34","0.3.35","0.3.4","0.3.5","0.3.6","0.3.7","0.3.8","0.3.9","0.4.0","0.4.0.dev1","0.4.0.dev2","0.4.1","0.4.2","0.4.3","0.4.4","0.4.5","0.4.6","0.4.6.dev1","0.4.7","0.4.8","0.5.0","0.5.0.dev1","0.5.0.dev2","0.5.1","0.5.10","0.5.11","0.5.12","0.5.13","0.5.14","0.5.15","0.5.16","0.5.17","0.5.18","0.5.19","0.5.2","0.5.20","0.5.3","0.5.3.dev1","0.5.4","0.5.5","0.5.6","0.5.7","0.5.8","0.5.9","0.6.0","0.6.1","0.6.10","0.6.11","0.6.12","0.6.13","0.6.14","0.6.15","0.6.16","0.6.18","0.6.19","0.6.2","0.6.20","0.6.21","0.6.22","0.6.23","0.6.24","0.6.25","0.6.26","0.6.26.dev1","0.6.27","0.6.28","0.6.29","0.6.3","0.6.30","0.6.31","0.6.32","0.6.33","0.6.34","0.6.35","0.6.36","0.6.37","0.6.38","0.6.39","0.6.4","0.6.40","0.6.41","0.6.42","0.6.43","0.6.5","0.6.6","0.6.6.dev1","0.6.7","0.6.8","0.6.9","0.7.0","0.7.1","0.7.2","0.8.0","0.8.1","0.8.10","0.8.11","0.8.12","0.8.2","0.8.3","0.8.4","0.8.5","0.8.6","0.8.7","0.8.8","0.8.9","0.9.0","0.9.1","0.9.2","0.9.3","0.9.4","0.9.5"]}],"products":[{"vendor":"open-webui","product":"open-webui"},{"vendor":"openwebui","product":"open_webui"}],"references":[{"url":"https://github.com/open-webui/open-webui/security/advisories/GHSA-v8qj-hxv7-mgvv","tags":["x_refsource_CONFIRM","exploit","Exploit","Mitigation","Vendor Advisory","advisory","web"]},{"url":"https://nvd.nist.gov/vuln/detail/CVE-2026-54011","tags":["advisory"]},{"url":"https://github.com/advisories/GHSA-v8qj-hxv7-mgvv","tags":["advisory"]},{"url":"https://github.com/open-webui/open-webui","tags":["package"]},{"url":"https://github.com/pypa/advisory-database/tree/main/vulns/open-webui/PYSEC-2026-2759.yaml","tags":["web"]},{"url":"https://pypi.org/project/open-webui","tags":["web","package"]},{"url":"https://github.com/CVEProject/cvelistV5/tree/main/cves/2026/54xxx/CVE-2026-54011.json","tags":["advisory"]}],"sources":{"cve":[{"id":"CVE-2026-54011","title":"Open WebUI: Stored XSS in Mermaid Markdown Preview","description":"Open WebUI is a self-hosted artificial intelligence platform designed to operate entirely offline. Prior to 0.9.6,Open WebUI renders Mermaid blocks from Markdown files in the file preview panel and inserts the generated SVG into the DOM using innerHTML. Because Mermaid is configured with securityLevel: 'loose', attacker-controlled Mermaid content can be rendered unsafely in this flow. A working payload was validated through the Markdown preview path, resulting in JavaScript execution in the victim’s browser under the application origin.  This vulnerability is fixed in 0.9.6.","status":"published","published":"2026-06-23T16:47:43.581Z","modified":"2026-06-23T17:55:33.824Z","cvss":[{"version":"3.1","score":8.7,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:N","level":"high","assessor":"cna"}],"cwes":["CWE-79"],"updated_at":"2026-11-02T13:38:09.774038Z"}],"euvd":[{"id":"EUVD-2026-38531","description":"Open WebUI is a self-hosted artificial intelligence platform designed to operate entirely offline. Prior to 0.9.6,Open WebUI renders Mermaid blocks from Markdown files in the file preview panel and inserts the generated SVG into the DOM using innerHTML. Because Mermaid is configured with securityLevel: 'loose', attacker-controlled Mermaid content can be rendered unsafely in this flow. A working payload was validated through the Markdown preview path, resulting in JavaScript execution in the victim’s browser under the application origin.  This vulnerability is fixed in 0.9.6.","status":"published","published":"2026-06-23T16:47:43Z","modified":"2026-06-23T17:55:33Z","cvss":[{"version":"3.1","score":8.7,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:N","level":"high"}],"updated_at":"2026-11-02T18:20:31.51905Z"}],"ghsa":[{"id":"GHSA-v8qj-hxv7-mgvv","title":"Open WebUI: Stored XSS in Mermaid Markdown Preview","description":"## Summary\n\nOpen WebUI renders Mermaid blocks from Markdown files in the file preview panel and inserts the generated SVG into the DOM using `innerHTML`.\n\nBecause Mermaid is configured with `securityLevel: 'loose'`, attacker-controlled Mermaid content can be rendered unsafely in this flow. A working payload was validated through the Markdown preview path, resulting in JavaScript execution in the victim’s browser under the application origin.\n\nThis is a confirmed stored XSS vulnerability reachable through normal product functionality.\n\n## Affected Version\n\n- `main`\n- Reproduced on `v0.8.12`\n\n## Affected Code\n\nMermaid is initialized in permissive mode:\n\nhttps://github.com/open-webui/open-webui/blob/9bd84258d09eefe7bf975878fb0e31a5dadfe0f8/src/lib/utils/index.ts#L1698\nThe file preview path renders Mermaid output and injects the returned SVG into the DOM:\n\nhttps://github.com/open-webui/open-webui/blob/9bd84258d09eefe7bf975878fb0e31a5dadfe0f8/src/lib/components/chat/FileNav/FilePreview.svelte#L133\n\n## Impact\n\nA successful exploit allows JavaScript execution in the victim’s browser under the Open WebUI origin when a malicious Markdown file is opened in the preview panel.\n\n## PoC\n\nA malicious `.md` file containing the follwowing contents can be used to trigger the bug:\n````\n```mermaid\nflowchart LR\n  A[click me]\n  click A href \"javascript:alert(document.domain)\" \"x\"\n```\n````\nSteps to reproduce: \n1- Create a new chat \n2- Enable Code Interpreter and browse and upload the file with `.md` extension. \n\u003cimg width=\"331\" height=\"258\" alt=\"image\" src=\"https://github.com/user-attachments/assets/bce2b754-56d1-4da1-90a9-22bcb93269f2\" /\u003e\n3- Clicking on the file, and clicking `click me` should pop an alert\n\u003cimg width=\"1103\" height=\"485\" alt=\"image\" src=\"https://github.com/user-attachments/assets/18754486-799b-434e-a2fc-dd7c09956a29\" /\u003e\n \n\n## Remediation\n\nSince `mermaid` has `DOMPurify` as a built-in, it is recommended to use the `strict` mode instead of `loose`.","status":"published","published":"2026-06-17T14:14:05Z","modified":"2026-07-20T21:04:31Z","cvss":[{"version":"3.1","score":8.7,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:N","level":"high"}],"cwes":["CWE-79"],"updated_at":"2026-11-02T14:40:47.245721Z"}],"nvd":[{"id":"CVE-2026-54011","description":"Open WebUI is a self-hosted artificial intelligence platform designed to operate entirely offline. Prior to 0.9.6,Open WebUI renders Mermaid blocks from Markdown files in the file preview panel and inserts the generated SVG into the DOM using innerHTML. Because Mermaid is configured with securityLevel: 'loose', attacker-controlled Mermaid content can be rendered unsafely in this flow. A working payload was validated through the Markdown preview path, resulting in JavaScript execution in the victim’s browser under the application origin.  This vulnerability is fixed in 0.9.6.","status":"published","published":"2026-06-23T18:18:06.31Z","modified":"2026-06-25T13:33:32.057Z","cvss":[{"version":"3.1","score":8.7,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:N","level":"high","assessor":"secondary"},{"version":"3.1","score":5.4,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N","level":"medium","assessor":"primary"}],"cwes":["CWE-79"],"updated_at":"2026-11-02T14:12:25.288279Z"}],"osv":[{"id":"CVE-2026-54011","title":"Open WebUI: Stored XSS in Mermaid Markdown Preview","description":"Open WebUI is a self-hosted artificial intelligence platform designed to operate entirely offline. Prior to 0.9.6,Open WebUI renders Mermaid blocks from Markdown files in the file preview panel and inserts the generated SVG into the DOM using innerHTML. Because Mermaid is configured with securityLevel: 'loose', attacker-controlled Mermaid content can be rendered unsafely in this flow. A working payload was validated through the Markdown preview path, resulting in JavaScript execution in the victim’s browser under the application origin.  This vulnerability is fixed in 0.9.6.","status":"published","published":"2026-06-23T16:47:43.581Z","modified":"2026-10-28T02:31:08.436338879Z","cvss":[{"version":"3.1","score":8.7,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:N","level":"high"}],"cwes":["CWE-79"],"updated_at":"2026-11-02T15:45:08.132336Z"},{"id":"GHSA-v8qj-hxv7-mgvv","title":"Open WebUI: Stored XSS in Mermaid Markdown Preview","description":"## Summary\n\nOpen WebUI renders Mermaid blocks from Markdown files in the file preview panel and inserts the generated SVG into the DOM using `innerHTML`.\n\nBecause Mermaid is configured with `securityLevel: 'loose'`, attacker-controlled Mermaid content can be rendered unsafely in this flow. A working payload was validated through the Markdown preview path, resulting in JavaScript execution in the victim’s browser under the application origin.\n\nThis is a confirmed stored XSS vulnerability reachable through normal product functionality.\n\n## Affected Version\n\n- `main`\n- Reproduced on `v0.8.12`\n\n## Affected Code\n\nMermaid is initialized in permissive mode:\n\nhttps://github.com/open-webui/open-webui/blob/9bd84258d09eefe7bf975878fb0e31a5dadfe0f8/src/lib/utils/index.ts#L1698\nThe file preview path renders Mermaid output and injects the returned SVG into the DOM:\n\nhttps://github.com/open-webui/open-webui/blob/9bd84258d09eefe7bf975878fb0e31a5dadfe0f8/src/lib/components/chat/FileNav/FilePreview.svelte#L133\n\n## Impact\n\nA successful exploit allows JavaScript execution in the victim’s browser under the Open WebUI origin when a malicious Markdown file is opened in the preview panel.\n\n## PoC\n\nA malicious `.md` file containing the follwowing contents can be used to trigger the bug:\n````\n```mermaid\nflowchart LR\n  A[click me]\n  click A href \"javascript:alert(document.domain)\" \"x\"\n```\n````\nSteps to reproduce: \n1- Create a new chat \n2- Enable Code Interpreter and browse and upload the file with `.md` extension. \n\u003cimg width=\"331\" height=\"258\" alt=\"image\" src=\"https://github.com/user-attachments/assets/bce2b754-56d1-4da1-90a9-22bcb93269f2\" /\u003e\n3- Clicking on the file, and clicking `click me` should pop an alert\n\u003cimg width=\"1103\" height=\"485\" alt=\"image\" src=\"https://github.com/user-attachments/assets/18754486-799b-434e-a2fc-dd7c09956a29\" /\u003e\n \n\n## Remediation\n\nSince `mermaid` has `DOMPurify` as a built-in, it is recommended to use the `strict` mode instead of `loose`.","status":"published","published":"2026-06-17T14:14:05Z","modified":"2026-07-20T21:15:24.578552416Z","cvss":[{"version":"3.1","score":8.7,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:N","level":"high"}],"cwes":["CWE-79"],"updated_at":"2026-11-02T15:46:56.981655Z"},{"id":"PYSEC-2026-2759","title":"Open WebUI: Stored XSS in Mermaid Markdown Preview","description":"## Summary\n\nOpen WebUI renders Mermaid blocks from Markdown files in the file preview panel and inserts the generated SVG into the DOM using `innerHTML`.\n\nBecause Mermaid is configured with `securityLevel: 'loose'`, attacker-controlled Mermaid content can be rendered unsafely in this flow. A working payload was validated through the Markdown preview path, resulting in JavaScript execution in the victim’s browser under the application origin.\n\nThis is a confirmed stored XSS vulnerability reachable through normal product functionality.\n\n## Affected Version\n\n- `main`\n- Reproduced on `v0.8.12`\n\n## Affected Code\n\nMermaid is initialized in permissive mode:\n\nhttps://github.com/open-webui/open-webui/blob/9bd84258d09eefe7bf975878fb0e31a5dadfe0f8/src/lib/utils/index.ts#L1698\nThe file preview path renders Mermaid output and injects the returned SVG into the DOM:\n\nhttps://github.com/open-webui/open-webui/blob/9bd84258d09eefe7bf975878fb0e31a5dadfe0f8/src/lib/components/chat/FileNav/FilePreview.svelte#L133\n\n## Impact\n\nA successful exploit allows JavaScript execution in the victim’s browser under the Open WebUI origin when a malicious Markdown file is opened in the preview panel.\n\n## PoC\n\nA malicious `.md` file containing the follwowing contents can be used to trigger the bug:\n````\n```mermaid\nflowchart LR\n  A[click me]\n  click A href \"javascript:alert(document.domain)\" \"x\"\n```\n````\nSteps to reproduce: \n1- Create a new chat \n2- Enable Code Interpreter and browse and upload the file with `.md` extension. \n\u003cimg width=\"331\" height=\"258\" alt=\"image\" src=\"https://github.com/user-attachments/assets/bce2b754-56d1-4da1-90a9-22bcb93269f2\" /\u003e\n3- Clicking on the file, and clicking `click me` should pop an alert\n\u003cimg width=\"1103\" height=\"485\" alt=\"image\" src=\"https://github.com/user-attachments/assets/18754486-799b-434e-a2fc-dd7c09956a29\" /\u003e\n \n\n## Remediation\n\nSince `mermaid` has `DOMPurify` as a built-in, it is recommended to use the `strict` mode instead of `loose`.","status":"published","published":"2026-07-13T15:46:19.301063Z","modified":"2026-07-13T16:32:24.951226218Z","cvss":[{"version":"3.1","score":8.7,"vector":"CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:N","level":"high"}],"updated_at":"2026-11-02T15:52:55.961245Z"}]}}