fix(deps): update dependency koa to v2.16.2 [security]

[renovate]

This PR contains the following updates:

Package	Change	Age	Confidence
koa (source)	2.16.1 -> 2.16.2

GitHub Vulnerability Alerts

CVE-2025-8129

Summary

In the latest version of Koa, the back method used for redirect operations adopts an insecure implementation, which uses the user-controllable referrer header as the redirect target.

Details

on the API document https://www.koajs.net/api/response#responseredirecturl-alt, we can see:

response.redirect(url, [alt])

Performs a [302] redirect to url.
The string "back" is specially provided for Referrer support, using alt or "/" when Referrer does not exist.

ctx.redirect('back');
ctx.redirect('back', '/index.html');
ctx.redirect('/login');
ctx.redirect('http://google.com');

however, the "back" method is insecure:

• https://github.com/koajs/koa/blob/master/lib/response.js#L322

  back (alt) {
    const url = this.ctx.get('Referrer') || alt || '/'
    this.redirect(url)
  },

Referrer Header is User-Controlled.

PoC

there is a demo for POC:

const Koa = require('koa')
const serve = require('koa-static')
const Router = require('@​koa/router')
const path = require('path')

const app = new Koa()
const router = new Router()

// Serve static files from the public directory
app.use(serve(path.join(__dirname, 'public')))

// Define routes
router.get('/test', ctx => {
  ctx.redirect('back', '/index1.html')
})

router.get('/test2', ctx => {
  ctx.redirect('back')
})

router.get('/', ctx => {
  ctx.body = 'Welcome to the home page! Try accessing /test, /test2'
})

app.use(router.routes())
app.use(router.allowedMethods())

const port = 3000
app.listen(port, () => {
  console.log(`Server running at http://localhost:${port}`)
}) 

Proof Of Concept

GET /test HTTP/1.1
Host: 127.0.0.1:3000
Referer: http://www.baidu.com
Connection: close

GET /test2 HTTP/1.1
Host: 127.0.0.1:3000
Referer: http://www.baidu.com
Connection: close

Impact

https://learn.snyk.io/lesson/open-redirect/

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Release Notes

koajs/koa (koa)

v2.16.2

Compare Source

What's Changed

• fix: only allow back redirect to the same origin referer by @​fengmk2 in https://github.com/koajs/koa/pull/1898

Full Changelog: koajs/koa@v2.16.1...v2.16.2

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