What is CVE-2018-20524?

CVE-2018-20524 is a medium-severity vulnerability in Urlchatbox Chat Anywhere, classified under Cross-site Scripting. CVSS score: 6.1/10. Published 2018-12-27.

How severe is CVE-2018-20524?

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

XSS in Urlchatbox Chat Anywhere

CVE-2018-20524

The Chat Anywhere extension 2.4.0 for Chrome allows XSS via crafted use of <<a> in a message, because a danmuWrapper DIV element in chatbox-only\danmu.js is outside the scope of a Content Security Policy (CSP).

Vulnerability class: XSS (Cross-Site Scripting)

Published 2018-12-27 · last modified 2026-06-17.

CVSS v3 metric

CVSS v3 base score 6.1 (Medium). Vector: CVSS:3.0/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N.

EPSS exploit prediction

EPSS: 0.007 (51.7th percentile), scored 2026-10-02.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 52nd percentile — 51.7% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.007 · newest: 0.007 · change: 0.000

Affected products

Urlchatbox Chat Anywhere — versions 2.4.0

Weakness classification (CWE)

CWE-79 — Cross-site Scripting

References

vul.su.ki/posts/Chat_Anywhere_2.4.0_XSS.md/ (Exploit, Third Party Advisory)

Frequently asked questions

What is CVE-2018-20524?: CVE-2018-20524 is a medium-severity vulnerability in Urlchatbox Chat Anywhere, classified under Cross-site Scripting. CVSS score: 6.1/10. Published 2018-12-27.
How severe is CVE-2018-20524?: Medium severity. CVSS v3 base score is 6.1 out of 10.