css-display-reading-polyfillnpm
Advisory published Updated
css-display-reading-polyfill is a confirmed malicious npm package (MAL-2026-17549) that typosquats a legitimate package to trick installs (malicious version 1.0.0). Do not install it — remove it immediately and rotate any exposed credentials.
Malicious code in css-display-reading-polyfill (npm)
What this malware does
The package ships payload.bundle.min.js, which on load runs an IIFE that invokes child_process.execSync to run id, whoami, and uname, collects os.hostname(), node version, process.platform, and pid, and transmits the results to the hardcoded collector https://webhook.site/5e52603d-f802-4a6f-b91b-43c3a5b45b6b via fetch and https.get. The published name impersonates an internal Wix thunderbolt module: shipped thunderbolt manifest JSON files declare this package as the loader entry for dozens of Wix component registry names (Container, StylableButton, MasterPage,...) and nine host registries (thunderboltRegistry, editorRegistry, corvidRegistry,...), with "shared":["payload.bundle.min.js"] and components mapped to that bundle. index.js is a benign stub; the exfil code lives entirely in the bundle, so any Wix runtime that resolves these internal registry names from this public package executes the host-reconnaissance payload. This is a dependency-confusion active attack: installer-side shell command output and host identifiers are sent to an attacker-controlled, non-first-party endpoint.
Malicious versions
Indicators of compromise (SHA-256)
Detection & response playbook
TyposquatFind it
Search your lockfiles and build artifacts for css-display-reading-polyfill (version 1.0.0).
If you installed it — respond
css-display-reading-polyfill is a typosquat — you almost certainly intended a legitimately-named package. Remove css-display-reading-polyfill, install the correct package, and rotate any secrets exposed during the install since post-install scripts may have already run.
Did it already run?
If css-display-reading-polyfill was installed, its post-install payload may already have run. Removing the package does not undo that — check outbound connections and credential use from the install window onward.
Frequently asked questions
Campaign
References
Credits
- Amazon Inspector · finder
Detect & block this
O3 blocks css-display-reading-polyfill-class packages before install and in CI — and if it already ran, its runtime egress monitoring catches the malicious outbound activity and severs the channel.