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CVE-2021-20663: Cross-site scripting vulnerability in in Role authority setting screen of Movable Type 7 r.4705 and earlier (M

36
Routine
MEDIUM 6.1UPGRADEUPGRADEUPGRADE

CVE-2021-20663 is a medium-severity flaw (CVSS 6.1) affecting movable type, movable type advanced, movable type premium. Below: why it ranks where it does, which versions are affected, what to do, and the exact commands.

Cross-site scripting vulnerability in in Role authority setting screen of Movable Type 7 r.4705 and earlier (Movable Type 7 Series), Movable Type Advanced 7 r.4705 and earlier (Movable Type Advanced 7 Series), Movable Type 6.7.5 and earlier (Movable Type 6.7 Series), Movable Type Premium 1.39 and earlier, and Movable Type Premium Advanced 1.39 and earlier allows remote attackers to inject an arbitrary script via unspecified vectors.

Why this priority

  • No elevated risk signals yet

A fixed release or distro patch exists.

Risk facts

CVSS score6.1 (Medium)
Attack vectorNetwork (remote)
Attack complexityLow
Privileges neededNone
User interactionRequired
EPSS exploit chance0.8% (top 42%)
CISA exploited listNo
WeaknessCWE-79
Published2021-03-05
Last modified2026-06-17
Publisher (CNA): JPCERT/CC · Vendor: movabletype

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

Am I affected?

Timeline

movabletype movable type UPGRADE
Affected: <= 6.7.5 · >= 7.0000 and <= 7.4705
Fixed in: newer than 7.4705
Safe to downgrade to: a release before 7.0000
1. Check installed version
apt-cache policy movable-type || rpm -q movable-type || movable-type --version
2. UPGRADE to newer than 7.4705 (Debian / Ubuntu)
sudo apt update && sudo apt install --only-upgrade movable-type
2. UPGRADE (RHEL / Amazon Linux / Fedora)
sudo dnf upgrade movable-type
Note
Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.
3. If no update is available yet, DOWNGRADE to a release before 7.0000 (Debian / Ubuntu)
apt-cache madison movable-type sudo apt install movable-type=<VERSION_BEFORE_7.0000> sudo apt-mark hold movable-type
3. If no update is available yet, DOWNGRADE (RHEL / Amazon Linux / Fedora)
dnf --showduplicates list movable-type sudo dnf downgrade movable-type-<VERSION_BEFORE_7.0000> sudo dnf versionlock add movable-type
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.
movabletype movable type advanced UPGRADE
Affected: <= 7.4705
Fixed in: newer than 7.4705
Safe to downgrade to: no unaffected older release
1. Check installed version
apt-cache policy movable-type-advanced || rpm -q movable-type-advanced || movable-type-advanced --version
2. UPGRADE to newer than 7.4705 (Debian / Ubuntu)
sudo apt update && sudo apt install --only-upgrade movable-type-advanced
2. UPGRADE (RHEL / Amazon Linux / Fedora)
sudo dnf upgrade movable-type-advanced
Note
Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.
movabletype movable type premium UPGRADE
Affected: <= 1.39
Fixed in: newer than 1.39
Safe to downgrade to: no unaffected older release
1. Check installed version
apt-cache policy movable-type-premium || rpm -q movable-type-premium || movable-type-premium --version
2. UPGRADE to newer than 1.39 (Debian / Ubuntu)
sudo apt update && sudo apt install --only-upgrade movable-type-premium
2. UPGRADE (RHEL / Amazon Linux / Fedora)
sudo dnf upgrade movable-type-premium
Note
Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.
movabletype movable type premium advanced UPGRADE
Affected: <= 1.39
Fixed in: newer than 1.39
Safe to downgrade to: no unaffected older release
1. Check installed version
apt-cache policy movable-type-premium-advanced || rpm -q movable-type-premium-advanced || movable-type-premium-advanced --version
2. UPGRADE to newer than 1.39 (Debian / Ubuntu)
sudo apt update && sudo apt install --only-upgrade movable-type-premium-advanced
2. UPGRADE (RHEL / Amazon Linux / Fedora)
sudo dnf upgrade movable-type-premium-advanced
Note
Distros often backport fixes without changing the version number. Confirm with the distro advisory or changelog.
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-2021-20663?

movable type: upgrade to newer than 7.4705; movable type advanced: upgrade to newer than 7.4705; movable type premium: upgrade to newer than 1.39. Exact commands for each OS are on this page.

Is CVE-2021-20663 being exploited?

CVE-2021-20663 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-2021-20663 affect?

CVE-2021-20663 affects movable type, movable type advanced, movable type premium. Severity is medium (CVSS 6.1). Cross-site scripting vulnerability in in Role authority setting screen of Movable Type 7 r.4705 and earlier (Movable Type 7 Series), Movable Type Advanced 7 r.4705 and earlier (Movable Type Advanced 7 Series), Movable Type 6.7.5 and earlier

How urgent is CVE-2021-20663?

Priority 36/100. No elevated risk signals yet.

Related CVEs

References

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