How severe is CVE-2021-20663?

CVE-2021-20663 has a CVSS 3.x base score of 6.1, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is low, integrity low, and availability none.

Is CVE-2021-20663 being actively exploited?

It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (52nd percentile), an estimate of the probability of exploitation in the next 30 days.

What products are affected by CVE-2021-20663?

CVE-2021-20663 primarily affects Movabletype Movable Type. In total, 4 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.

How do I fix CVE-2021-20663?

Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.

When was CVE-2021-20663 published?

CVE-2021-20663 was published on 2021-03-05 and last updated on 2026-06-17.

CVE-2021-20663

CVE-2021-20663 is a medium-severity vulnerability in Movabletype Movable Type with a CVSS 3.x base score of 6.1. It is not currently listed as actively exploited by CISA, and its EPSS exploit-prediction score is low. The underlying weakness is classified as CWE-79.

Key facts

Severity: Medium (CVSS 3.x base score 6.1)
CVSS v2: 4.3
EPSS exploit prediction: 1% (52nd percentile)
Actively exploited: Not listed in CISA KEV
Weakness: CWE-79
Affected product: Movabletype Movable Type
Published: 2021-03-05
Last modified: 2026-06-17

Description

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.

Frequently asked questions

What is CVE-2021-20663?: 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.
How severe is CVE-2021-20663?: CVE-2021-20663 has a CVSS 3.x base score of 6.1, rated medium severity. It is exploitable over network with low attack complexity, requires no privileges and user interaction. Impact on confidentiality is low, integrity low, and availability none.
Is CVE-2021-20663 being actively exploited?: It is not currently listed in CISA's KEV catalog. Its EPSS exploit-prediction score is 1% (52nd percentile), an estimate of the probability of exploitation in the next 30 days.
What products are affected by CVE-2021-20663?: CVE-2021-20663 primarily affects Movabletype Movable Type. In total, 4 product configurations (CPEs) are listed as vulnerable; see the affected-products list for the exact versions.
How do I fix CVE-2021-20663?: Review the linked vendor and NVD advisories for patched versions and mitigations, then upgrade or apply the recommended workaround.
When was CVE-2021-20663 published?: CVE-2021-20663 was published on 2021-03-05 and last updated on 2026-06-17.

References

Affected products (4)

cpe:2.3:a:movabletype:movable_type:*:*:*:*:*:*:*:*
cpe:2.3:a:movabletype:movable_type_advanced:*:*:*:*:*:*:*:*
cpe:2.3:a:movabletype:movable_type_premium:*:*:*:*:*:*:*:*
cpe:2.3:a:movabletype:movable_type_premium_advanced:*:*:*:*:*:*:*:*

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