Update dependency js-cookie to v3 [SECURITY]

[renovate]

This PR contains the following updates:

Package	Change	Age	Confidence
js-cookie	^2.2.0 → ^3.0.0

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JavaScript Cookie: Per-instance prototype hijack in assign() enables cookie-attribute injection

CVE-2026-46625 / GHSA-qjx8-664m-686j

More information

Details

Summary

js-cookie's internal assign() helper copies properties with for...in + plain assignment. When the source object is produced by JSON.parse, the JSON object's "__proto__" member is an own enumerable property, so the for…in enumerates it and the target[key] = source[key] write triggers the Object.prototype.__proto__ setter on the fresh target ({}). The result is a per-instance prototype hijack: Object.prototype itself is untouched, but the merged attributes object now inherits attacker-controlled keys.

Because the consuming set() function then enumerates the merged object with another for...in, every key the attacker placed on the polluted prototype lands in the resulting Set-Cookie string as an attribute pair. The attacker can set domain=, secure=, samesite=, expires=, and path= on cookies whose attributes the developer thought were locked down.

Impact

Any application that forwards a JSON-derived object as the attributes argument to Cookies.set, Cookies.remove, Cookies.withAttributes, or Cookies.withConverter is vulnerable. This is the standard pattern when cookie configuration comes from a backend:

const cfg = await fetch('/config').then(r => r.json());
Cookies.set('session', token, cfg.cookieAttrs);   // cfg.cookieAttrs influenced by attacker

A payload of {"__proto__":{"domain":"evil.example","secure":"false","samesite":"None"}} causes js-cookie to emit:

Set-Cookie: session=TOKEN; path=/; domain=evil.example; secure=false; samesite=None

Affected code

// src/assign.mjs — full file
export default function (target) {
  for (var i = 1; i < arguments.length; i++) {
    var source = arguments[i]
    for (var key in source) {                 // includes own enumerable '__proto__'
      target[key] = source[key]                // [[Set]] form - fires __proto__ setter
    }
  }
  return target
}

Proof of concept

Node 22.11.0, no third-party deps:

Environment setup

mkdir -p /tmp/jscookie-poc && cd /tmp/jscookie-poc
npm init -y
npm i js-cookie

PoC

ubuntu@kuber:/tmp/jscookie-poc$ cat poc.mjs
let lastSetCookie = '';
globalThis.document = {
  get cookie() { return ''; },
  set cookie(v) { lastSetCookie = v; }
};

const { default: Cookies } = await import('js-cookie');

const attackerAttrs = JSON.parse(
  '{"__proto__":{"secure":"false","domain":"evil.com","samesite":"None","expires":-1}}'
);

Cookies.set('session', 'TOKEN', attackerAttrs);

console.log('Set-Cookie that js-cookie wrote to document.cookie:');
console.log(lastSetCookie);

Execution:

Suggested patch

--- a/src/assign.mjs
+++ b/src/assign.mjs
@@
 export default function (target) {
   for (var i = 1; i < arguments.length; i++) {
     var source = arguments[i]
-    for (var key in source) {
-      target[key] = source[key]
-    }
+    for (var key in source) {
+      if (key === '__proto__' || key === 'constructor' || key === 'prototype') continue
+      Object.defineProperty(target, key, {
+        value: source[key],
+        writable: true,
+        enumerable: true,
+        configurable: true,
+      })
+    }
   }
   return target
 }

Equivalent one-liner alternative - iterate own names only and filter:

for (const key of Object.getOwnPropertyNames(source)) {
  if (key === '__proto__') continue
  target[key] = source[key]
}

Severity

• CVSS Score: 7.5 / 10 (High)
• Vector String: CVSS:3.1/AV:N/AC:L/PR:N/UI:N/S:U/C:N/I:H/A:N

References

• https://github.com/js-cookie/js-cookie/security/advisories/GHSA-qjx8-664m-686j
• https://nvd.nist.gov/vuln/detail/CVE-2026-46625
• https://github.com/js-cookie/js-cookie/commit/eb3c40e89731e99b8970faaf35ddad249c6c0020
• https://github.com/js-cookie/js-cookie/releases/tag/v3.0.7
• https://github.com/advisories/GHSA-qjx8-664m-686j

This data is provided by the GitHub Advisory Database (CC-BY 4.0).

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Release Notes

js-cookie/js-cookie (js-cookie)

v3.0.7

Compare Source

• Prevent cookie attribute injection: CVE-2026-46625 (eb3c40e)
• Add Partitioned attribute to readme (b994768)
• Publish to npm registry via trusted publisher exclusively (4dc71be)
• Ensure consistent behaviour for get('name') + get() (1953d30)

v3.0.6

Compare Source

v3.0.5

Compare Source

• Remove npm version restriction in package.json - #​818

v3.0.4

Compare Source

• Publish to npmjs.com with package provenance

v3.0.3

Compare Source

v3.0.2

Compare Source

v3.0.1

Compare Source

• Make package.json accessible in export - #​727

v3.0.0

Compare Source

• Removed defaults in favor of a builder: now to supply an api instance with particular predefined (cookie) attributes there's Cookies.withAttributes(), e.g.:

const api = Cookies.withAttributes({
  path: '/',
  secure: true
})
api.set('key', 'value') // writes cookie with path: '/' and secure: true...

• The attributes that an api instance is configured with are exposed as attributes property; it's an immutable object and unlike defaults cannot be changed to configure the api.
• The mechanism to fall back to the standard, internal converter by returning a falsy value in a custom read converter has been removed. Instead the default converters are now exposed as Cookies.converter, which allows for implementing self-contained custom converters providing the same behavior:

const customReadConverter = (value, name) => {
  if (name === 'special') {
    return unescape(value)
  }
  return Cookies.converter.read(value)
}

• withConverter() no longer accepts a function as argument to be turned into a read converter. It is now required to always pass an object with the explicit type(s) of converter(s):

const api = Cookies.withConverter({
  read: (value, name) => unescape(value)
})

• The converter(s) that an api instance is configured with are exposed as converter property; it's an immutable object and cannot be changed to configure the api.
• Started providing library as ES module, in addition to UMD module. The module field in package.json points to an ES module variant of the library.
• Started using browser field instead of main in package.json (for the UMD variant of the library).
• Dropped support for IE < 10.
• Removed built-in JSON support, i.e. getJSON() and automatic stringifying in set(): use Cookies.set('foo', JSON.stringify({ ... })) and JSON.parse(Cookies.get('foo')) instead.
• Removed support for Bower.
• Added minified versions to package - #​501
• Improved support for url encoded cookie values (support case insensitive encoding) - #​466, #​530
• Expose default path via API - #​541
• Handle falsy arguments passed to getters - #​399
• No longer support Node < 12 when building (LTS versions only)

v2.2.1

Compare Source

• #​400: Prevent XSS in the cookie attributes
• #​350: Document npm package manager usage

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