CVE-2026-27737: BigBlueButton has Stored XSS in bbb-playback replay

Severity: medium (CVSS 6.5 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: 2026-05-18 · updated 2026-07-24
Weakness: CWE-79

Description

BigBlueButton is an open-source virtual classroom. In versions prior to 3.0.19, the recording playback (presentation format) was not sanitizing user's input in public chat. This allowed for a malicious actor to craft and carry out a targeted XSS attack, activated on anyone replaying the recording. This issue has been fixed 3.0.19.

Affected products

bigbluebutton bbb-playback: before 5.4.3
bigbluebutton: before 3.0.19
blindsidenetworks scalite: before 1.7.0

References

https://github.com/bigbluebutton/bbb-playback/commit/09e89bfe4ff8488b68c3ff040d3081e419dc89b1
https://github.com/bigbluebutton/bigbluebutton/commit/69f45aa1b963dc7d80179d0155acc670aec5c4fc
https://github.com/bigbluebutton/bigbluebutton/releases/tag/v3.0.19
https://github.com/bigbluebutton/bigbluebutton/security/advisories/GHSA-8vv7-vj94-q2pv
https://github.com/blindsidenetworks/scalelite/releases/tag/v1.7.0

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