Koa is expressive middleware for Node.js using ES2017 async functions. In koa < 2.16.1 and < 3.0.0-alpha.5, passing untrusted user input to ctx.redirect() even after sanitizing it, may execute javascript code on the user who use the app. This issue is patched in 2.16.1 and 3.0.0-alpha.5.
https://github.com/koajs/koa/security/advisories/GHSA-x2rg-q646-7m2v
https://github.com/koajs/koa/commit/ff25eb4a7f2392df46481fe86355161067687312