Highlight Js syntax highlighter security updates, in plain English

Highlight Js syntax highlighter

228 sites report using it · on drupal.org · 1 security update explained here

This module allows editors to display computer code with coloured text to make it easier to read.

Below is every security update for Highlight Js syntax highlighter that this site has covered, newest first. Each one says who could exploit it, whether it applies to your site, how urgent it is, and what to tell your developer. If your site uses this module and you are not sure which version, that is the first question to ask whoever looks after it.

Highlight Js syntax highlighter

Critical · 228 sites report using it · SA-CONTRIB-2026-299 · on drupal.org · Week of 4 November 2026

The module does not properly check text sent to its preview page. Anyone could use this to run unwanted scripts in the browser. This might allow them to view private details or modify existing content.

Who could do thisAnyone visiting the site. No login needed.
Does it apply to youAny site using this module.
Has it been used in attacksNo sign of it.
How urgentDrupal rates this critical. Cyber Essentials expects a fix within 14 days. Do it this week.

Tell your developerUpdate Highlight Js syntax highlighter to 1.3.1.

For developers: what the fix changed

The fix decodes the JSON configuration and validates it as an array in HighlightJsPreview.php, and forces the text configuration to a string in LanguageSelect.php to prevent render array injection.

1.3.0 to 1.3.1 1 commit, 2 files.

src/Controller/HighlightJsPreview.php +5 −1 fix
src/Plugin/HighlightJs/LanguageSelect.php +4 −1 fix

Full diff, 1.3.0 to 1.3.1

The comparison is against the release immediately before the fix. If your site is on an older release, more will have changed.

Get in touch

Tell me who you are, what your organisation does, and what you need. That might be a Drupal site that needs looking after, an upgrade to get done before December, or an agency that needs Drupal cover.

If I can help, I'll say so and suggest a call. If I can't, I'll tell you straight away rather than waste your time.

For context: I work mainly with UK membership bodies, charities and research organisations, and with the agencies that look after their websites. Not recruiters.

Or start smaller and connect with me on LinkedIn. That's where I post what I find digging around in charity and grants data, and where the free tools turn up first.

Highlight Js syntax highlighter

Highlight Js syntax highlighter

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