GHSA-hmx5-qpq5-p643 Prototype pollution in swiper

• npm swiper: >= 6.5.1, < 12.1.2 → fixed in 12.1.2

Summary A prototype pollution vulnerability exists in the the npm package swiper (>=6.5.1, -1; let obj = {}; var malicious_payload = '{"__proto__":{"polluted":"yes"}}'; console.log({}.polluted); swiper.default.extendDefaults(JSON.parse(malicious_payload)); console.log({}.polluted); // prints yes -> indicating that the patch was bypassed and prototype pollution occurred ``` Expected behavior Prototype pollution should be prevented and {} should not gain new properties. This should be printed on the console: ``` undefined undefined OR throw an Error ``` Actual behavior Object.prototype is polluted This is printed on the console: ``` undefined yes ``` Impact This is a prototype pollution vulnerability, which can have severe security implications depending on how swiper is used by downstream applications. Any application that processes attacker-controlled input using this package may be affected. It could potentially lead to the following problems: 1. Authentication bypass 2. Denial of service - Even if an attacker is not able to exploit prototype pollution in swiper, if there is a prototype pollution within the project from other dependencies, modifying global `Array.prototype.indexOf` property can result in crash when swiper.default.extendDefaults is called because swiper makes use of this global property. This can lead to Denial of Service. 3. Remote code execution (if polluted property is passed to sinks like eval or child_process) Related CVEs CVE-2026-25521 CVE-2026-25047 CVE-2026-26021