What is CVE-2020-21353?

CVE-2020-21353 is a medium-severity vulnerability in Get-Simple Getsimplecms, classified under Cross-site Scripting. CVSS score: 5.4/10. Published 2021-08-06.

How severe is CVE-2020-21353?

Medium severity. CVSS v3 base score is 5.4 out of 10.

XSS in Get-Simple Getsimplecms

CVE-2020-21353

A stored cross site scripting (XSS) vulnerability in /admin/snippets.php of GetSimple CMS 3.4.0a allows attackers to execute arbitrary web scripts or HTML via crafted payload in the Edit Snippets module.

Vulnerability class: XSS (Cross-Site Scripting)

Published 2021-08-06 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 5.4 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N.

EPSS exploit prediction

EPSS: 0.005 (43.9th percentile), scored 2026-10-02.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 44th percentile — 43.9% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.005 · newest: 0.005 · change: 0.000

Affected products

Get-Simple Getsimplecms — versions 3.4.0a

Weakness classification (CWE)

CWE-79 — Cross-site Scripting

References

github.com/GetSimpleCMS/GetSimpleCMS/issues/1319 (Exploit, Third Party Advisory)

Frequently asked questions

What is CVE-2020-21353?: CVE-2020-21353 is a medium-severity vulnerability in Get-Simple Getsimplecms, classified under Cross-site Scripting. CVSS score: 5.4/10. Published 2021-08-06.
How severe is CVE-2020-21353?: Medium severity. CVSS v3 base score is 5.4 out of 10.