CVE-2021-29944Public exploitNetwork attack vector

HTML injection via unescaped Reader View attributes

Published Jun 24, 2021 · Updated Aug 3, 2024

HTML injection in Firefox for Android before 88 allows remote attackers to alter Reader View content through a crafted webpage. Reader View inserts the article dir value and other decoded fields into unquoted HTML attributes without complete escaping. A user must open the attacker-controlled page and enable Reader View; CSP blocks direct script execution, while injected markup can trigger requests or redirect the view under the original address.

CVSS severity6.1
Medium
EPSS probability0.70%
Next 30 days · Sep 16, 2026
Known exploitationUnconfirmed
Based on sourced intelligence
Hinoki checkNot available
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Summary

What happened

HTML injection in Firefox for Android before 88 allows remote attackers to alter Reader View content through a crafted webpage. Reader View inserts the article dir value and other decoded fields into unquoted HTML attributes without complete escaping. A user must open the attacker-controlled page and enable Reader View; CSP blocks direct script execution, while injected markup can trigger requests or redirect the view under the original address.

The record

CVE
CVE-2021-29944
Published
Jun 24, 2021
Updated
Aug 3, 2024
Vendor
Mozilla
Product
Firefox
Classifications
CWE-79
Attack vector
network
Privileges
unauthenticated

Timeline

How it unfolded

  1. Jun 24, 2021CVE publishedPublication date reported by the CVE source.
  2. Aug 3, 2024Record updatedLatest update available in the CVE record.

Exploitability

Present is not the same as exploitable

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Is a vulnerable build present?

Compare these published version ranges with your installed build and any vendor patches.

  1. Affected versionversion=unspecified <88

What conditions does exploitation require?

Attack vectornetwork
Required privilegesunauthenticated

What is affected?

Mozilla · Firefoxversion=unspecified <88

Published CVSS scores

6.1NIST NVDCVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N
4.3NIST NVDAV:N/AC:M/Au:N/C:N/I:P/A:N

CVSS describes severity. EPSS estimates exploitation probability.

Attacks

What attackers are doing with it

Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.

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No observations available

Sep 10, 2026Sep 16, 2026
Latest reporting daySep 16, 2026
Latest daily unique IPsUnavailable
Prior 30-day averageUnavailable
SourceShadowserver honeypots (KEV)
Vectornetwork
Privilegesunauthenticated
Known exploitationUnconfirmed
Public exploitPublished

Weakness, pattern, technique

CWE-79Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')

Public exploit references

Labels summarize the accepted research assessment. They do not indicate a test against your environment.

Technologies

Your stack

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Your stack

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