CVE-2026-9309

Arbitrary JavaScript execution in internal pages via Reader View JSON-LD injection

MEDIUM
5.4
CVSS Score
Published: June 1, 2026 at 11:24 AM UTC
Updated: July 22, 2026 at 07:37 AM UTC
1 product affected across 1 vendorFirefox

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Severity
MEDIUM5.4
Exploit prediction
EPSS 0.2%
SSVC
No known exploit

Description

Firefox for iOS Reader View did not properly escape HTML tags in JSON-LD metadata. A malicious page could inject markup that changed Reader View behavior and leaked sensitive URL parameters. These parameters could then be used to access internal pages, potentially resulting in arbitrary JavaScript execution in an internal origin. This vulnerability was fixed in Firefox for iOS 151.2.

Affected

Our own answer: ranges merged, affected separated from platform-only, with confidence and review flags.

v < 151.2
Vendor states this is fixed in 151.2 (unaffected)

Remediation

No guide yet

No remediation guidance has been written for this CVE yet. What the record does show:

References (2)

SSVC — Action Prioritization

SSVCNo known exploitNot automatablePartial impact

SSVC signals action urgency (what to patch first), separate from CVSS which measures severity.

CVSS

5.4MEDIUMCISA-ADP
Attack Vector
NETWORK
Complexity
LOW
Privileges
NONE
User Interaction
REQUIRED
Scope
UNCHANGED
Confidentiality
LOW
Integrity
LOW
Availability
NONE
Vector?

Quick Info

StatusANALYZED
CWE
CWE-79

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