What is CVE-2026-71555?

CVE-2026-71555 is a medium-severity vulnerability in Thm-Health Pilos, classified under Use of Web Link to Untrusted Target with window.opener Access. CVSS score: 4.1/10. Published 2026-08-06.

How severe is CVE-2026-71555?

Medium severity. CVSS v3 base score is 4.1 out of 10.

Vulnerability in Thm-Health Pilos

CVE-2026-71555

PILOS (Platform for Interactive Live-Online Seminars) is a frontend for BigBlueButton. From 2.1.0 until 4.14.1, PILOS does not send a Cross-Origin-Opener-Policy response header, so pages opened by PILOS via a link that opens a new browsing context (e.g., target="_blank") retain a window.opener reference back to the originating PILOS tab. A malicious destination page reached this way can use window.opener to navigate or manipulate the original PILOS tab, a technique known as reverse tabnabbing, potentially redirecting an authenticated user to a phishing page that mimics PILOS. This issue is fixed in version 4.14.1.

EPSS: 0.002 (6.5th percentile) — read the EPSS interpretation.

CVSS v3 metric

CVSS v3 base score 4.1 (Medium). Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:N/I:L/A:N.

Affected products

Thm-health Pilos — versions >= 2.1.0, < 4.14.1

Weakness classification (CWE)

CWE-1022 — Use of Web Link to Untrusted Target with window.opener Access

References

security-advisories@github.com (x_refsource_MISC)
security-advisories@github.com (x_refsource_MISC)
security-advisories@github.com (x_refsource_CONFIRM)

Frequently asked questions

What is CVE-2026-71555?: CVE-2026-71555 is a medium-severity vulnerability in Thm-Health Pilos, classified under Use of Web Link to Untrusted Target with window.opener Access. CVSS score: 4.1/10. Published 2026-08-06.
How severe is CVE-2026-71555?: Medium severity. CVSS v3 base score is 4.1 out of 10.