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CVE-2026-71555: PILOS: Reverse tabnabbing in room description

• Severity: medium (CVSS 4.1 v3.1)
• Exploited in the wild: not listed in CISA KEV
• EPSS: 0.3% probability of exploitation in the next 30 days
• Public exploit or detection template: none known
• Published: 2026-08-06 · updated 2026-10-24
• Weakness: CWE-1022

Description

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.

Affected products

• THM-Health PILOS: from 2.1.0, < 4.14.1

References

• https://github.com/THM-Health/PILOS/commit/b50f2bd07c4f4a7d6a9981578238ae3579275d81
• https://github.com/THM-Health/PILOS/releases/tag/v4.14.1
• https://github.com/THM-Health/PILOS/security/advisories/GHSA-j4wr-p8gh-xrw5

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