What is CVE-2018-1000855?

CVE-2018-1000855 is a medium-severity vulnerability in Basecamp Easymon, classified under Cross-site Scripting. CVSS score: 6.1/10. Published 2018-12-20.

How severe is CVE-2018-1000855?

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

XSS in Basecamp Easymon

CVE-2018-1000855

easymon version 1.4 and earlier contains a Cross Site Scripting (XSS) vulnerability in Endpoint where monitoring is mounted that can result in Reflected XSS that affects Firefox. Can be used to steal cookies, depending on the cookie settings.. This attack appear to be exploitable via The victim must click on a crafted URL that contains the XSS payload. This vulnerability appears to have been fixed in 1.4.1 and later.

Vulnerability class: XSS (Cross-Site Scripting)

Published 2018-12-20 · 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: 0.009 (58.0th percentile), scored 2026-09-29.

Very low probability of exploitation in the next 30 days; routine patching cadence is appropriate. 58th percentile — 58.0% of CVEs in the catalogue have a lower EPSS than this one. How to read EPSS.

EPSS over last 30 days · oldest: 0.009 · newest: 0.009 · change: 0.000

Affected products

Basecamp Easymon

Weakness classification (CWE)

CWE-79 — Cross-site Scripting

References

github.com/basecamp/easymon/pull/25 (Patch, Third Party Advisory)
github.com/basecamp/easymon/issues/26 (Patch, Third Party Advisory)

Frequently asked questions

What is CVE-2018-1000855?: CVE-2018-1000855 is a medium-severity vulnerability in Basecamp Easymon, classified under Cross-site Scripting. CVSS score: 6.1/10. Published 2018-12-20.
How severe is CVE-2018-1000855?: Medium severity. CVSS v3 base score is 6.1 out of 10.