CVE-2020-9440: A cross-site scripting (XSS) vulnerability in the WSC plugin through 5.5.7.5 for CKEditor 4 allows remote atta

Q: How do I fix CVE-2020-9440?

ckeditor: downgrade or apply the listed mitigation; webspellchecker: upgrade to newer than 5.5.7.5; fedora: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.

Q: Is CVE-2020-9440 being exploited?

CVE-2020-9440 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

Q: What does CVE-2020-9440 affect?

CVE-2020-9440 affects ckeditor, webspellchecker, fedora. Severity is medium (CVSS 6.1). A cross-site scripting (XSS) vulnerability in the WSC plugin through 5.5.7.5 for CKEditor 4 allows remote attackers to run arbitrary web script inside an IFRAME element by injecting a crafted HTML element into the editor.

Q: How urgent is CVE-2020-9440?

Priority 39/100. No elevated risk signals yet.

Routine

MEDIUM 6.1DOWNGRADEUPGRADEMITIGATE

CVE-2020-9440 is a medium-severity flaw (CVSS 6.1) affecting ckeditor, webspellchecker, fedora. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

A cross-site scripting (XSS) vulnerability in the WSC plugin through 5.5.7.5 for CKEditor 4 allows remote attackers to run arbitrary web script inside an IFRAME element by injecting a crafted HTML element into the editor.

Why this priority

No elevated risk signals yet

A fixed release or distro patch exists.

Risk facts

CVSS score	6.1 (Medium)
Attack vector	Network (remote)
Attack complexity	Low
Privileges needed	None
User interaction	Required
EPSS exploit chance	1.3% (top 29%)
CISA exploited list	No
Weakness	CWE-79
Published	2020-03-10
Last modified	2026-06-17

Publisher (CNA): MITRE · Vendor: ckeditor · fedoraproject · webspellchecker

Last updated 2026-06-17 · Sources: CVE Program, NVD, CISA KEV, EPSS and vendor advisories · How we score

Am I affected?

Timeline

2020-03-10 17:15 UTCPublished CVE record published
2026-06-17 03:27 UTCUpdated Record last modified

ckeditor ckeditor DOWNGRADE

Affected: 4.0

Fixed in: no fixed release known

Safe to downgrade to: a release before 4.0

1. Check installed version

apt-cache policy ckeditor || rpm -q ckeditor || ckeditor --version

2. No fixed release: DOWNGRADE to a release before 4.0 (Debian / Ubuntu)

apt-cache madison ckeditor sudo apt install ckeditor=<VERSION_BEFORE_4.0> sudo apt-mark hold ckeditor

2. No fixed release: DOWNGRADE (RHEL / Amazon Linux / Fedora)

dnf --showduplicates list ckeditor sudo dnf downgrade ckeditor-<VERSION_BEFORE_4.0> sudo dnf versionlock add ckeditor

Downgrade risk

Downgrading can break dependent software and may reopen older bugs. Read the distro advisory first and test on a non-production host.

After downgrade

Restart the service, and keep the package held until a fixed release ships.

webspellchecker webspellchecker UPGRADE

Affected: <= 5.5.7.5

Fixed in: newer than 5.5.7.5

Safe to downgrade to: no unaffected older release

1. Check installed version

apt-cache policy webspellchecker || rpm -q webspellchecker || webspellchecker --version

2. UPGRADE to newer than 5.5.7.5 (Debian / Ubuntu)

sudo apt update && sudo apt install --only-upgrade webspellchecker

2. UPGRADE (RHEL / Amazon Linux / Fedora)

sudo dnf upgrade webspellchecker

Note

Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.

fedoraproject fedora MITIGATE

Affected: 30 · 31 · 32

Fixed in: no fixed release known

Safe to downgrade to: a release before 30

Check your OS release

cat /etc/os-release; uname -r

Debian / Ubuntu

sudo apt update && sudo apt full-upgrade

RHEL / Amazon Linux / Fedora

sudo dnf upgrade --refresh

Windows

Install the latest cumulative update from Windows Update

If no patch exists yet

OS downgrades are not safe. Apply the vendor mitigation from the advisory and restrict exposure.

Verify at the official source NVD · CVE Program · Report a problem with this page
Scores and fixes here are computed automatically from those and other public sources. Confirm with the vendor advisory before changing production systems.

Quick answers

How do I fix CVE-2020-9440?

ckeditor: downgrade or apply the listed mitigation; webspellchecker: upgrade to newer than 5.5.7.5; fedora: mitigate or apply the listed mitigation. Exact commands for each OS are on this page.

Is CVE-2020-9440 being exploited?

CVE-2020-9440 is not on the CISA Known Exploited Vulnerabilities list at the time of the last update. Check again, as this can change.

What does CVE-2020-9440 affect?

CVE-2020-9440 affects ckeditor, webspellchecker, fedora. Severity is medium (CVSS 6.1). A cross-site scripting (XSS) vulnerability in the WSC plugin through 5.5.7.5 for CKEditor 4 allows remote attackers to run arbitrary web script inside an IFRAME element by injecting a crafted HTML element into the editor.

How urgent is CVE-2020-9440?

Priority 39/100. No elevated risk signals yet.

Related CVEs

CVE-2021-41164 HIGH 8.2 UPGRADE UPGRADE CKEditor4 is an open source WYSIWYG HTML editor
CVE-2021-26272 MEDIUM 6.5 UPGRADE DOWNGRADE It was possible to execute a ReDoS-type attack inside CKEditor 4 before 4.16 by persuading a victim to paste c
CVE-2021-26271 MEDIUM 6.5 UPGRADE DOWNGRADE It was possible to execute a ReDoS-type attack inside CKEditor 4 before 4.16 by persuading a victim to paste c
CVE-2020-27193 MEDIUM 6.1 DOWNGRADE DOWNGRADE A cross-site scripting (XSS) vulnerability in the Color Dialog plugin for CKEditor 4.15.0 allows remote attack
CVE-2023-31541 CRITICAL 9.8 DOWNGRADE A unrestricted file upload vulnerability was discovered in the ‘Browse and upload images’ feature of the CKEdi

References

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