Twig: The `spaceless` filter implicitly marks its output as safe
Description
The spaceless filter is registered with is_safe => ['html'], which means Twig's autoescaper does not escape its output in an HTML context. As a result, applying spaceless to attacker-controlled input that contains markup emits the markup unescaped even when the developer never wrote |raw and autoescape is enabled.
Example:
{% set payload = '<script>alert()</script>' %}
{{ payload }} {# escaped #}
{{ payload|spaceless }} {# not escaped #}The filter is deprecated but still functional. With the deprecation, some downstream projects (e.g. Drupal modules) have duplicated the filter and inherited the same is_safe flag.
Resolution
The spaceless filter no longer marks its output as safe. Documentation has been updated to warn that spaceless should not be applied to unsanitised user input.
Credits
Twig would like to thank Pierre Rudloff for reporting the issue.
Affected software
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| Platform | Package | Vulnerable versions | Fixed in |
|---|---|---|---|
| Composer package | twig/twig | < 3.26.0 | 3.26.0 |
References
- CVSS vector
CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N/E:U- Weakness (CWE)
CWE-116- Platform
- Composer
- Package
twig/twig- Disclosed
- 21.05.2026
- Updated
- 11.10.2026 10:22
Sources and licenses
OSV / GitHub Advisory Database - GHSA-4j38-f5cw-54h7 - CC BY 4.0
Vulnerability history: twig/twig
All published vulnerabilities of this package (Composer package), newest first. Shows whether this is a one-off slip or a package that needs watching.
- Total entries
- 24
- First → latest
- 02.2022 07.2026
- Without a fix
- 0
- Exploited in attacks
- 0
Severity breakdown
- Critical 1
- High 8
- Medium 8
- Low 7
Disclosures per year
- 2022: 4
- 2023: 0
- 2024: 4
- 2025: 1
- 2026: 15
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Twig: The `spaceless` filter implicitly marks its output as safe this entry
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