CVE-2021-20663

Name: CVE-2021-20663
Creator: NVD / NIST
Published: 2021-03-05T10:15:12.627+00:00
License: https://creativecommons.org/publicdomain/zero/1.0/

MEDIUMCVSS 6.1/10EPSS 0.81%

Last modified Jun 17, 2026

CVE-2021-20663 is a medium-severity vulnerability rated 6.1/10 on the CVSS scale. 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.. EPSS estimates a 0.81% chance of exploitation in the next 30 days.

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.

Metrics

CVSS 3.1

6.1/10

CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

EPSS Probability

0.81%

52.2th percentile

Probability of exploitation in the next 30 days. Learn more

Weakness Enumeration

CWE-79

Affected Software

Vendor	Product	Versions
Movabletype	Movable Type	<= 6.7.5
Movabletype	Movable Type	>= 7.0000, <= 7.4705
Movabletype	Movable Type Advanced	<= 7.4705
Movabletype	Movable Type Premium	<= 1.39
Movabletype	Movable Type Premium Advanced	<= 1.39

References

https://jvn.jp/en/jp/JVN66542874/index.htmlThird Party Advisory
https://movabletype.org/news/2021/02/mt-760-676-released.htmlRelease Notes, Vendor Advisory
https://jvn.jp/en/jp/JVN66542874/index.htmlThird Party Advisory
https://movabletype.org/news/2021/02/mt-760-676-released.htmlRelease Notes, Vendor Advisory

Timeline

Published: Mar 5, 2021
Last Modified: Jun 17, 2026
Status: Modified

Frequently Asked Questions

What is CVE-2021-20663?

How severe is CVE-2021-20663?

CVE-2021-20663 has a CVSS score of 6.1/10 (MEDIUM severity). The EPSS model estimates a 0.81% probability of exploitation in the next 30 days.

How do I fix CVE-2021-20663?

Check the vendor references and advisories linked above for patched versions and mitigation guidance. You can also run a Strix scan to test if your systems are affected.

Are you affected by CVE-2021-20663?

Run a free Strix scan to check your systems for this vulnerability.

Scan your code now

Source: NVD / NIST