GHSA-3r53-75j5-3g7j: Quasar: Prototype pollution in the extend() utility

Summary quasar@2.20.1, the latest published version at the time of testing, appears to be vulnerable to prototype pollution through the public extend() utility exported from the package root. When extend(true, target, source) is used for a deep merge, attacker-controlled object keys are recursively copied into the target object without blocking prototype-pollution primitives such as proto, constructor, or prototype. This can allow attacker-controlled properties to be written to Object.prototype. Details Affected source: src/utils/extend/extend.js Distributed files include: dist/quasar.server.prod.js dist/quasar.server.prod.cjs dist/quasar.client.js The package root publicly exports extend. During deep merge, source object keys are recursively assigned into the target object. If the source object contains an own proto property, the merge can descend into the prototype object and assign attacker-controlled properties onto Object.prototype. PoC rm -rf /tmp/quasar-extend-pp-poc mkdir /tmp/quasar-extend-pp-poc cd /tmp/quasar-extend-pp-poc npm init -y >/dev/null npm install quasar@2.20.1 vue@3.5.31 >/dev/null cat > hack.mjs <<'JS' import { extend } from 'quasar'; delete Object.prototype.polluted; extend(true, {}, { ['proto']: { polluted: 'yes' } }); console.log(({}).polluted); delete Object.prototype.polluted; JS node ./hack.mjs Observed output: yes Expected output: undefined Impact This is a prototype pollution vulnerability. If an application passes user-controlled or partially user-controlled objects into extend(true, ...), an attacker may be able to pollute Object.prototype in the same JavaScript process. Depending on how the polluted property is later consumed, this may lead to logic bypass, unsafe default option injection, denial of service, or other application-specific security impact. Suggested Fix Reject or safely ignore dangerous keys before assignment, including: proto prototype constructor The merge implementation should also avo