SWC HTML minifier may allow script element breakout when minifying embedded JSON

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SWC is a TypeScript / JavaScript compiler written in Rust. Prior to @swc/html 1.15.47-nightly-20260729.1 and swc_html_minifier 59.0.0, the minifyJson processing in crates/swc_html_minifier/src/lib.rs parsed and serialized attacker-controlled JSON in application/json and application/ld+json script elements without the escape_json_for_html_script behavior to re-escape less-than signs, allowing a closing script sequence to terminate the element early and execute script in the generated page's origin. This issue is fixed in @swc/html 1.15.47-nightly-20260729.1 and swc_html_minifier 59.0.0.

Source published

11 Aug 2026 14:45:12 UTC

Source modified

11 Aug 2026 18:26:38 UTC

Saved here

23 Oct 2026 15:48:27 UTC

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CVE Program Terms of Use

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CVSS 3.1 · 6.1 CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

SWC is a TypeScript / JavaScript compiler written in Rust. Prior to @swc/html 1.15.47-nightly-20260729.1 and swc_html_minifier 59.0.0, the minifyJson processing in crates/swc_html_minifier/src/lib.rs parsed and serialized attacker-controlled JSON in application/json and application/ld+json script elements without the escape_json_for_html_script behavior to re-escape less-than signs, allowing a closing script sequence to terminate the element early and execute script in the generated page's origin. This issue is fixed in @swc/html 1.15.47-nightly-20260729.1 and swc_html_minifier 59.0.0.

Source published

Aug 11, 2026, 2:45:12 PM (timezone not stated)

Source modified

Aug 11, 2026, 6:26:38 PM (timezone not stated)

Saved here

11 Nov 2026 16:04:01 UTC

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EUVD CVSS 3.1 · 6.1 CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

SWC is a TypeScript / JavaScript compiler written in Rust. Prior to @swc/html 1.15.47-nightly-20260729.1 and swc_html_minifier 59.0.0, the minifyJson processing in crates/swc_html_minifier/src/lib.rs parsed and serialized attacker-controlled JSON in application/json and application/ld+json script elements without the escape_json_for_html_script behavior to re-escape less-than signs, allowing a closing script sequence to terminate the element early and execute script in the generated page's origin. This issue is fixed in @swc/html 1.15.47-nightly-20260729.1 and swc_html_minifier 59.0.0.

Source published

11 Aug 2026 15:17:38 UTC

Source modified

18 Sep 2026 20:05:53 UTC

Saved here

25 Oct 2026 15:19:03 UTC

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CVSS 3.1 · [email protected] · Secondary · 6.1 CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

## Impact `@swc/html` minifies JSON contained in `script` elements such as `application/json` and `application/ld+json` by parsing and serializing the JSON value. Before the patched versions, JSON serialization could convert escaped less-than signs such as `\u003C` into literal `<` characters. If the JSON contained an escaped `</script>` sequence, the generated HTML could terminate the containing script element early because HTML tokenization occurs before the JSON is consumed. Applications that minify HTML containing attacker-controlled JSON data could therefore transform inert data into active markup. A crafted payload could execute script in the origin of the generated page. ## Patches The issue is fixed in: - `@swc/html` 1.15.47 - `swc_html_minifier` 59.0.0 The minifier now re-escapes less-than signs after JSON serialization, preserving the script element boundary. ## Workarounds Users who cannot upgrade can disable JSON minification with: ```js await minify(html, { minifyJson: false, });

Source published

8 Sep 2026 17:58:00 UTC

Source modified

8 Sep 2026 18:15:03 UTC

Saved here

24 Oct 2026 13:17:17 UTC

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GitHub Advisory Database · CC-BY-4.0

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CVSS_V3 · CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:N

Publisher rating · MODERATE