SiYuan: Stored XSS in Bazaar marketplace via package README event handlers

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.

SiYuan is an open-source personal knowledge management system. Prior to 3.7.0, renderPackageREADME in kernel/bazaar/readme.go renders a Bazaar package README from Markdown to HTML with the lute engine and SetSanitize(true). The lute sanitizer is an event-handler blocklist: allowAttr rejects only attribute names present in a fixed eventAttrs map copied from the w3schools legacy handler list. That map omits modern event handlers. onpointerover, onpointerdown, onauxclick, onbeforetoggle, onfocusin, onanimationstart, and ontransitionend are not in the list, so the sanitizer passes them through verbatim on any tag. The frontend assigns the rendered HTML to mdElement.innerHTML in app/src/config/bazaar.ts with no client-side DOMPurify on this path, into a normal element in the main document (no iframe, no sandbox). The kernel sends no Content-Security-Policy, X-Frame-Options, or X-Content-Type-Options header on any response, so an inline handler runs when its event fires. The README is rendered when an Administrator opens a package in Settings → Marketplace, after the one-time marketplace trust consent. Install is not required. Result: a third-party Bazaar package author runs JavaScript in the Administrator's authenticated SiYuan origin when the Administrator views and interacts with the package listing, and gains full control of the workspace. This vulnerability is fixed in 3.7.0.

Source published

24 Jun 2026 21:18:24 UTC

Source modified

26 Jun 2026 18:43:38 UTC

Observed here

23 Oct 2026 15:48:27 UTC

Source terms

CVE Program Terms of Use

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: cve-program · CVE Program Terms of Use. Source text is retained; field grouping and change labels are provided by ChangeIntel.

CVSS 3.1 · 7.1 CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:L

SiYuan is an open-source personal knowledge management system. Prior to 3.7.0, renderPackageREADME in kernel/bazaar/readme.go renders a Bazaar package README from Markdown to HTML with the lute engine and SetSanitize(true). The lute sanitizer is an event-handler blocklist: allowAttr rejects only attribute names present in a fixed eventAttrs map copied from the w3schools legacy handler list. That map omits modern event handlers. onpointerover, onpointerdown, onauxclick, onbeforetoggle, onfocusin, onanimationstart, and ontransitionend are not in the list, so the sanitizer passes them through verbatim on any tag. The frontend assigns the rendered HTML to mdElement.innerHTML in app/src/config/bazaar.ts with no client-side DOMPurify on this path, into a normal element in the main document (no iframe, no sandbox). The kernel sends no Content-Security-Policy, X-Frame-Options, or X-Content-Type-Options header on any response, so an inline handler runs when its event fires. The README is rendered when an Administrator opens a package in Settings → Marketplace, after the one-time marketplace trust consent. Install is not required. Result: a third-party Bazaar package author runs JavaScript in the Administrator's authenticated SiYuan origin when the Administrator views and interacts with the package listing, and gains full control of the workspace. This vulnerability is fixed in 3.7.0.

Source published

Jun 24, 2026, 9:18:24 PM (timezone not stated)

Source modified

Jun 26, 2026, 6:43:38 PM (timezone not stated)

Observed here

7 Nov 2026 12:28:20 UTC

Source terms

ENISA EUVD · source terms and attribution apply

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

SiYuan is an open-source personal knowledge management system. Prior to 3.7.0, renderPackageREADME in kernel/bazaar/readme.go renders a Bazaar package README from Markdown to HTML with the lute engine and SetSanitize(true). The lute sanitizer is an event-handler blocklist: allowAttr rejects only attribute names present in a fixed eventAttrs map copied from the w3schools legacy handler list. That map omits modern event handlers. onpointerover, onpointerdown, onauxclick, onbeforetoggle, onfocusin, onanimationstart, and ontransitionend are not in the list, so the sanitizer passes them through verbatim on any tag. The frontend assigns the rendered HTML to mdElement.innerHTML in app/src/config/bazaar.ts with no client-side DOMPurify on this path, into a normal element in the main document (no iframe, no sandbox). The kernel sends no Content-Security-Policy, X-Frame-Options, or X-Content-Type-Options header on any response, so an inline handler runs when its event fires. The README is rendered when an Administrator opens a package in Settings → Marketplace, after the one-time marketplace trust consent. Install is not required. Result: a third-party Bazaar package author runs JavaScript in the Administrator's authenticated SiYuan origin when the Administrator views and interacts with the package listing, and gains full control of the workspace. This vulnerability is fixed in 3.7.0.

Source published

24 Jun 2026 22:16:48 UTC

Source modified

25 Oct 2026 23:10:00 UTC

Observed here

27 Oct 2026 14:13:29 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 · 7.1 CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:L

## Summary `renderPackageREADME` in `kernel/bazaar/readme.go` renders a Bazaar package README from Markdown to HTML with the lute engine and `SetSanitize(true)`. The lute sanitizer is an event-handler blocklist: `allowAttr` rejects only attribute names present in a fixed `eventAttrs` map copied from the w3schools legacy handler list. That map omits modern event handlers. `onpointerover`, `onpointerdown`, `onauxclick`, `onbeforetoggle`, `onfocusin`, `onanimationstart`, and `ontransitionend` are not in the list, so the sanitizer passes them through verbatim on any tag. The frontend assigns the rendered HTML to `mdElement.innerHTML` in `app/src/config/bazaar.ts` with no client-side DOMPurify on this path, into a normal element in the main document (no iframe, no sandbox). The kernel sends no Content-Security-Policy, X-Frame-Options, or X-Content-Type-Options header on any response, so an inline handler runs when its event fires. The README is rendered when an Administrator opens a package in Settings → Marketplace, after the one-time marketplace trust consent. Install is not required. Result: a third-party Bazaar package author runs JavaScript in the Administrator's authenticated SiYuan origin when the Administrator views and interacts with the package listing, and gains full control of the workspace. ## Affected siyuan-note/siyuan, `<= 3.6.5` (latest release, 2026-04-21). Confirmed live-exploitable on the `b3log/siyuan:v3.6.5` image; identical code on `master` HEAD. Condition: the Administrator has accepted the marketplace trust consent (`bazaar.trust`, default false) and browses community Bazaar packages. The lute dependency pin is `github.com/88250/lute v1.7.7-0.20260419134724-bb68012f231d`. Both the online browse path (`getBazaarPackageREADME`) and the installed-package path (`getInstalledPlugin`) reach the same sink. ## Root cause `render/sanitizer.go:225-232` (lute): `allowAttr(name)` returns false only when `name` exists in the `eventAttrs` map, an attribute denylist rather than an allowlist. `render/sanitizer.go:235-334` (lute): `eventAttrs` is the w3schools handler list and contains no pointer, beforetoggle, focusin, animation, or transition handlers. `kernel/bazaar/readme.go:108-118`: `renderPackageREADME` builds the engine with `SetSanitize(true)` and returns the HTML string to the caller. `kernel/bazaar/readme.go:48-88`: `GetBazaarPackageREADME` renders an untrusted remote package README; `kernel/api/bazaar.go` exposes it at `/api/bazaar/getBazaarPackageREADME` (`router.go:423`, `CheckAuth`). `app/src/config/bazaar.ts:600` and `:609`: `mdElement.innerHTML = data.preferredReadme` / `= response.data.html`, no DOMPurify, target is a plain div. Kernel HTTP responses carry no CSP/X-Frame-Options/X-Content-Type-Options header (live-confirmed), so an inline handler is not blocked. ## Reproduction `b3log/siyuan:v3.6.5` Docker, default config, access auth code set, marketplace trust accepted. 1. Place a package whose README carries a non-blocklisted handler (an online community package produces the identical render at browse time): ``` mkdir -p workspace/data/plugins/evil-plugin cat > workspace/data/plugins/evil-plugin/plugin.json <<'JSON' {"name":"evil-plugin","author":"x","version":"1.0.0","minAppVersion":"3.0.0", "displayName":{"default":"Evil"},"description":{"default":"poc"}, "readme":{"default":"README.md"},"backends":["all"],"frontends":["all"]} JSON printf '<div onpointerover="alert(document.domain)">plugin description</div>\n' \ > workspace/data/plugins/evil-plugin/README.md ``` 2. Request the rendered README the way the Marketplace panel does: ``` curl -s -X POST http://127.0.0.1:6806/api/bazaar/getInstalledPlugin \ -H "Authorization: Token <API-TOKEN>" -H "Content-Type: application/json" \ -d '{"frontend":"all","keyword":""}' ``` Response `data.packages[].preferredReadme` contains the handler verbatim: ``` <div onpointerover="alert(document.domain)">plugin description</div> ``` A control `<img src=x onerror=...>` in the same README is returned HTML-escaped and inert. 3. In Settings → Marketplace, open the package and move the pointer over its README. Live-verified: the rendered HTML is assigned to `mdElement.innerHTML` (no CSP, no sandbox) and the `onpointerover` handler executes `alert(document.domain)` in the SiYuan origin on hover. Handlers do not auto-fire on insertion; one pointer/focus/click interaction on the listing triggers them. ## Impact - JavaScript execution in the Administrator's authenticated origin on a marketplace package view plus one hover/click/focus, no install needed. - Theft of the kernel API token (`conf.api.token`), which grants full Administrator API access. - Pivot to `installBazaarPlugin` and kernel control; the runtime image ships a shell. - A single malicious community package reaches every instance that views its listing. ## Credit Jan Kahmen, [turingpoint](https://turingpoint.de) ([email protected])

Source published

10 Jul 2026 19:27:24 UTC

Source modified

21 Jul 2026 19:19:25 UTC

Observed here

24 Oct 2026 13:19:41 UTC

Source terms

GitHub Advisory Database · CC-BY-4.0

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: 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:H/PR:N/UI:R/S:U/C:H/I:H/A:L

Publisher rating · HIGH

SiYuan: Stored XSS in Bazaar marketplace via package README event handlers in github.com/siyuan-note/siyuan/kernel

Source published

17 Jul 2026 19:42:05 UTC

Source modified

21 Jul 2026 19:15:30 UTC

Observed here

24 Oct 2026 13:19:41 UTC

Source terms

OSV · upstream source license applies

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: osv · OSV · upstream source license applies. Source text is retained; field grouping and change labels are provided by ChangeIntel.