CVE-2021-30533: in the CISA KEV catalogue
Google Chromium PopupBlocker Security Bypass Vulnerability. CISA added CVE-2021-30533 to the Known Exploited Vulnerabilities catalogue on 2022-06-27 with a default due date of 2022-07-18. Known ransomware campaign use: Unknown. Forensic triage flag: No.
Google Chromium PopupBlocker contains an insufficient policy enforcement vulnerability that allows a remote attacker to bypass navigation restrictions via a crafted iframe. This vulnerability could affect multiple web browsers that utilize Chromium, including, but not limited to, Google Chrome, Microsoft Edge, and Opera. (CISA description)
- Vendor / product
- Google Chromium PopupBlocker
- CWE
- CWE-863
- CISA required action
- Apply updates per vendor instructions.
- EPSS
- 17%, percentile 97 (scored 2026-11-03)
EPSS puts about 17 in 100 odds (17%) on exploitation activity being observed in the next 30 days. Its score is higher than or equal to that of 97% of scored CVEs. This is a model estimate about exploitation anywhere, not about your environment.
Vendor and reference links (from CISA)
Your own deadline under CISA BOD 26-04 depends on exposure, automatability and technical impact: work it out with the BOD 26-04 calculator.
Frequently asked questions
Is CVE-2021-30533 in the CISA KEV catalogue?
Yes. CISA added CVE-2021-30533 (Google Chromium PopupBlocker Security Bypass Vulnerability) to the Known Exploited Vulnerabilities catalogue on 2022-06-27. CISA's default due date for it is 2022-07-18.
Is CVE-2021-30533 used in ransomware attacks?
CISA marks known ransomware campaign use as Unknown for CVE-2021-30533. That means CISA lacks confirmation, not that ransomware groups do not use it.
What should I do about CVE-2021-30533?
CISA's required action: Apply updates per vendor instructions.
Sources
- CISA, Known Exploited Vulnerabilities Catalog (accessed 2026-11-03)
- FIRST, Exploit Prediction Scoring System (EPSS) (EPSS by FIRST; scores generated by Empirical Security)
- NVD record for CVE-2021-30533