🚨 [security] Update swiper 8.4.7 → 12.1.2 (major)

[depfu]

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🚨 Your current dependencies have known security vulnerabilities 🚨

This dependency update fixes known security vulnerabilities. Please see the details below and assess their impact carefully. We recommend to merge and deploy this as soon as possible!

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Here is everything you need to know about this upgrade. Please take a good look at what changed and the test results before merging this pull request.

What changed?

✳️ swiper (8.4.7 → 12.1.2) · Repo · Changelog

Security Advisories 🚨

🚨 Prototype pollution in swiper

Summary

A prototype pollution vulnerability exists in the the npm package swiper (>=6.5.1, < 12.1.2). Despite a previous fix that attempted to mitigate prototype pollution by checking whether user input contained a forbidden key, it is still possible to pollute Object.prototype via a crafted input using Array.prototype. The exploit works across Windows and Linux and on Node and Bun runtimes. This issue is fixed in version 12.1.2

Details

The vulnerability resides in line 94 of shared/utils.mjs where indexOf() function is used to check whether user provided input contain forbidden strings.

PoC

Steps to reproduce

1. Install latest version of swiper using npm install
2. Run the following code snippet:

var swiper = require('swiper');
Array.prototype.indexOf = () => -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

Release Notes

Too many releases to show here. View the full release notes.

Commits

See the full diff on Github. The new version differs by 2 commits:

• 12.1.2
• fix prototype pollution bypass in extend() util

🗑️ dom7 (removed)

🗑️ ssr-window (removed)

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