Threats / Google / CVE-2021-30533
CVE-2021-30533
· EUVD no mirror located
· GCVE no mirror located
Verified 2026-08-04
Google Chromium PopupBlocker vulnerability
Google Chromium PopupBlocker contains insufficient policy enforcement allowing remote attackers to bypass navigation restrictions via crafted iframes, affecting multiple Chromium-based browsers.
Verdict
Today item — known-exploited.
A remote attacker can craft a malicious iframe to circumvent popup blocking policies in Chromium-based browsers, potentially enabling unwanted navigation and content delivery to users without proper security controls.
CISA KEV Yes · 2022-06-274EPSS 0.16611 (verify live)5CVSS 6.5 (CISA)3CISA SSVC Exploitation: active · Automatable: no · Impact: partial3
01
Is it exploitable?
— the evidence, ranked above the scoreReported exploitation
2 independent public reports of in-the-wild exploitation are cataloged.Distinct reporting sources (vendor, incident response, government); open them for the underlying claims.
Exploited in the wild
Listed in the CISA Known Exploited Vulnerabilities catalog (added 2022-06-27).
Probability (EPSS)
EPSS 0.16611 — modeled likelihood of exploitation activity.EPSS is a daily-changing model output — open the source for today's value.
Severity / affected
CVSS 6.5 (CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:N/I:H/A:N) · Affected: Google, Chromium PopupBlocker. Confirm exact fixed builds in the vendor advisory.CVSS — CISA-assigned via the ADP container (CVE.org), version 3.1; the CNA left no metrics, so CISA's own score is used ahead of NVD.
Weakness (CWE)
Mapped to CWE-863 Incorrect Authorization — weakness family: Authorization / access control.CWE assignment from the public NVD record (may be stale); the weakness class drives how the flaw is exploited.
CISA SSVC (triage disposition)
Exploitation: active · Automatable: no · Technical Impact: partialCISA's own stakeholder-specific triage inputs, published in the CVE record (CISA Coordinator role). NOTE: this is CISA's three decision points; the final Act/Attend/Track decision also requires a Mission & Well-being input not published here, so no overall decision is asserted.
Currency of the record
CISA added this to its KEV catalog 385 days after the CVE record was published.KEV lag = CISA-KEV dateAdded − CVE.org datePublished; a floor on how long the known-exploited flaw sat in the public record before the federal catalog listed it. Severity/weakness here is CNA- or CISA-assigned (current at disclosure), independent of NVD's analysis backlog.
02
Who’s exploiting it?
— attribution turns risk into urgencyAttribution not established
No confirmed (advisory-backed) threat-actor attribution is established for this record. Absence of a named actor is not absence of compromise — see Coverage & confidence.
03
Why it matters
— the attack path, told twice: adversary, then board1
Front door — unauthenticated access narrative 1
Attacker
I craft a malicious webpage containing an iframe designed to exploit the PopupBlocker policy enforcement gap.
Business
Users are exposed to uncontrolled navigation and potentially malicious content that should have been blocked by security policies.
2
Keys to the kingdom — privilege/identity takeover narrative 2
Attacker
I host the exploit on a website and distribute it through social engineering or advertising networks to reach target users.
Business
Browser vendors face reputation damage and user trust erosion due to security policy bypass in their products.
3
Lateral reach — past segmentation narrative 3
Attacker
I redirect users to phishing sites, malware distribution points, or unwanted advertising through the bypassed popup restrictions.
Business
Organizations experience increased support costs and potential liability for user compromise resulting from inadequate browser security controls.
04
What to do
— defensible action- Remediate per the vendor advisory — confirm the fixed build for your version and verify exposure.1
Say it to the boardA vulnerability with this evidence profile is a defensible budget line, not a backlog ticket — fund the change against the proof above.
05