What is CVE-2020-5528?

CVE-2020-5528 is a medium-severity vulnerability in Sixapart Movable Type, classified under Cross-site Scripting. CVSS score: 6.1/10. Published 2020-02-06.

How severe is CVE-2020-5528?

Medium severity. CVSS v3 base score is 6.1 out of 10.

XSS in Sixapart Movable Type

CVE-2020-5528

Cross-site scripting vulnerability in Movable Type series (Movable Type 7 r.4603 and earlier (Movable Type 7), Movable Type 6.5.2 and earlier (Movable Type 6.5), Movable Type Advanced 7 r.4603 and earlier (Movable Type Advanced 7), Movable Type Advanced 6.5.2 and earlier (Movable Type Advanced 6.5), Movable Type Premium 1.26 and earlier (Movable Type Premium), and Movable Type Premium Advanced 1.26 and earlier (Movable Type Premium Advanced)) allows remote attackers to inject arbitrary web script or HTML in the block editor and the rich text editor via a specially crafted URL.

Vulnerability class: XSS (Cross-Site Scripting)

Published 2020-02-06 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 6.1 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N.

EPSS exploit prediction

EPSS: 0.008 (56.2th percentile), scored 2026-09-29.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 56th percentile — 56.2% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.008 · newest: 0.008 · change: 0.000

Affected products

Sixapart Movable Type
Six Apart Ltd Movable Type Series — versions Movable Type 7 r.4603 and earlier (Movable Type 7), Movable Type 6.5.2 and earlier (Movable Type 6.5), Movable Type Advanced 7 r.4603 and earlier (Movable Type Advanced 7), Movable Type Advanced 6.5.2 and earlier (Movable Type Advanced 6.5), Movable Type Premium 1.26 and earlier (Movable Type Premium), and Movable Type Premium Advanced 1.26 and earlier (Movable Type Premium Advanced)

Weakness classification (CWE)

CWE-79 — Cross-site Scripting

References

movabletype.org/news/2020/02/movable_type_r4605_v720_v653_and_v6311_released.ht… (Third Party Advisory)
jvn.jp/en/jp/JVN94435544/index.html (Third Party Advisory)

Frequently asked questions

What is CVE-2020-5528?: CVE-2020-5528 is a medium-severity vulnerability in Sixapart Movable Type, classified under Cross-site Scripting. CVSS score: 6.1/10. Published 2020-02-06.
How severe is CVE-2020-5528?: Medium severity. CVSS v3 base score is 6.1 out of 10.