axios npm Supply Chain Attack — March 31, 2026

March 31, 2026 · PackageFix · Breaking · Updated as new information emerges

What happened

On March 31, 2026, an attacker compromised the npm account of the primary axios maintainer and published two malicious versions of axios — one of the most widely-used JavaScript libraries with approximately 100 million weekly downloads.

The malicious versions did not modify axios source code directly. Instead, they added a hidden dependency — plain-crypto-js@4.2.1 — to the package.json. When npm installed axios@1.14.1, it automatically pulled in plain-crypto-js@4.2.1 and executed its postinstall hook. That script was a RAT dropper targeting macOS, Windows, and Linux.

# Check your current axios version
npm list axios

# Check if plain-crypto-js is present
grep -r "plain-crypto-js" package-lock.json

# If affected - downgrade immediately
npm install axios@1.14.0

# For 0.x users
npm install axios@0.30.3

# Commit the fix
git add package.json package-lock.json
git commit -m "security: downgrade axios - supply chain attack (GHSA-fw8c-xr5c-95f9)"

How the attack worked

The attack was pre-staged 18 hours in advance. plain-crypto-js@4.2.0 was published on March 30 as a clean decoy to establish a brief package history and avoid "brand-new package" alarms from security scanners. plain-crypto-js@4.2.1 containing the payload was then published just before the malicious axios releases.

The dropper used two layers of obfuscation: reversed Base64 encoding with padding substitution, and XOR cipher with a hardcoded key. After execution, it deleted itself and replaced its package.json with a clean decoy — leaving no obvious trace in node_modules for a developer inspecting after the fact.

Attack timeline

Indicators of Compromise (IOCs)

Why axios was targeted

axios is present in approximately 80% of cloud and code environments. It is a direct or transitive dependency in millions of applications. The attacker targeted the 1.x and 0.x branches simultaneously to maximize exposure across both modern and legacy codebases. The attack appears to be espionage or APT activity — no cryptocurrency mining or ransomware components were found, suggesting credential harvesting and intelligence gathering rather than immediate financial gain.

How PackageFix helps

Paste your package-lock.json into PackageFix. If your lockfile resolves axios@1.14.1 or axios@0.30.4, PackageFix will flag it as malicious and show the safe downgrade version. It also detects plain-crypto-js@4.2.1 as a known malicious package via the OSV database.