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CVE-2026-9308

Arbitrary JavaScript execution in Reader View due to wrong HTML replacement order

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 replaced page content in its HTML template before replacing other internal placeholders. A malicious page could include a placeholder string that was later substituted with JSON-LD data, potentially resulting in arbitrary JavaScript execution. 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.

Firefox· Mozilla
95%
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:

Patch and advisory references

References (2)

Permissions Required
Source: cverecord
https://bugzilla.mozilla.org/show_bug.cgi?id=2039422
Vendor Advisory
Source: cverecord
https://www.mozilla.org/security/advisories/mfsa2026-53/

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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