CVE-2017-20202

critical

Description

Web Developer for Chrome v0.4.9 contained malicious code that generated a domain via a DGA and fetched a remote script. The fetched script conditionally loaded follow-on modules that performed extensive ad substitution and malvertising, displayed fake “repair” alerts that redirected users to affiliate programs, and attempted to harvest credentials when users logged in. Injected components enumerate common banner sizes for substitution, replace third-party ad calls, and redirect victim traffic to affiliate landing pages. Potential impacts include user-level code execution in the browser context, large-scale ad fraud and traffic hijacking, credential theft, and exposure to additional payloads delivered by the actor. The compromise was reported on by the maintainer of Web Developer for Chrome on August 2, 2017 and remediated in v0.5.0.

References

https://www.vulncheck.com/advisories/web-developer-for-chrome-malicious-backdoor-supply-chain-compromise

https://www.proofpoint.com/us/threat-insight/post/threat-actor-goes-chrome-extension-hijacking-spree

https://web.archive.org/web/20170803163618/https://chrispederick.com/blog/web-developer-for-chrome-compromised/

https://ui.vision/blog/chrome-extension-adware/

https://gist.github.com/piedpiperRichard/076516da60f45842f1a6e6ae35a9a240/

https://chromewebstore.google.com/detail/web-developer/bfbameneiokkgbdmiekhjnmfkcnldhhm?pli=1

Details

Source: Mitre, NVD

Published: 2025-10-08

Updated: 2025-10-14

Risk Information

CVSS v2

Base Score: 7.5

Vector: CVSS2#AV:N/AC:L/Au:N/C:P/I:P/A:P

Severity: High

CVSS v3

Base Score: 9.8

Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:N/S:U/C:H/I:H/A:H

Severity: Critical

CVSS v4

Base Score: 9.3

Vector: CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:A/VC:H/VI:H/VA:N/SC:H/SI:H/SA:N

Severity: Critical

EPSS

EPSS: 0.00078