CVE-2021-41258

Kirby is an open source file structured CMS. In affected versions Kirby's blocks field stores structured data for each block. This data is then used in block snippets to convert the blocks to HTML for use in your templates. We recommend to escape HTML special characters to protect against cross-site scripting (XSS) attacks. The default snippet for the image block unfortunately did not use our escaping helper. This made it possible to include malicious HTML code in the source, alt and link fields of the image block, which would then be displayed on the site frontend and executed in the browsers of site visitors and logged in users who are browsing the site. Attackers must be in your group of authenticated Panel users in order to exploit this weakness. Users who do not make use of the blocks field are not affected. This issue has been patched in Kirby version 3.5.8 by escaping special HTML characters in the output from the default image block snippet. Please update to this or a later version to fix the vulnerability.

Kirby is an open source file structured CMS. In affected versions Kirby's blocks field stores structured data for each block. This data is then used in block snippets to convert the blocks to HTML for use in your templates. We recommend to escape HTML special characters to protect against cross-site scripting (XSS) attacks. The default snippet for the image block unfortunately did not use our escaping helper. This made it possible to include malicious HTML code in the source, alt and link fields of the image block, which would then be displayed on the site frontend and executed in the browsers of site visitors and logged in users who are browsing the site. Attackers must be in your group of authenticated Panel users in order to exploit this weakness. Users who do not make use of the blocks field are not affected. This issue has been patched in Kirby version 3.5.8 by escaping special HTML characters in the output from the default image block snippet. Please update to this or a later version to fix the vulnerability.

### Impact Kirby's [blocks field](https://getkirby.com/docs/reference/panel/fields/blocks) stores structured data for each block. This data is then used in [block snippets](https://getkirby.com/docs/reference/panel/fields/blocks#block-snippets) to convert the blocks to HTML for use in your templates. We recommend to [escape HTML special characters](https://getkirby.com/docs/guide/templates/escaping) against cross-site scripting (XSS) attacks. Cross-site scripting (XSS) is a type of vulnerability that allows to execute any kind of JavaScript code inside the site frontend or Panel session of other users. If the user is logged in to the Panel, a harmful script can for example trigger requests to Kirby's API with the permissions of the victim. The default snippet for the [image block](https://getkirby.com/docs/reference/panel/blocks/image) unfortunately did not use our escaping helper. This made it possible to include malicious HTML code in the source, alt and link fields of the image block, which would then be displayed on the site frontend and executed in the browsers of site visitors and logged in users who are browsing the site. This vulnerability is critical if you might have potential attackers in your group of authenticated Panel users. They can escalate their privileges if they get access to the Panel session of an admin user. Depending on your site, other JavaScript-powered attacks are possible. You are *not* affected if you don't use the blocks field or specifically the image block in any of your blueprints. You are also protected if you use a custom [block snippet](https://getkirby.com/docs/reference/panel/fields/blocks#block-snippets) that either escapes the printed values or doesn't use them. The attack can only be performed by logged-in users and only surfaces in the site frontend (i.e. in your templates). The Panel itself is unaffected and will not execute JavaScript that was injected into the image block content. ### Patches We have patched the vulnerability in [Kirby 3.5.8](https://github.com/getkirby/kirby/releases/tag/3.5.8) by escaping special HTML characters in the output from the default image block snippet. Please update to this or a [later version](https://github.com/getkirby/kirby/releases/) to fix the vulnerability. ### Credits Thanks to Azrul Ikhwan Zulkifli (@azrultech) from BAE Systems AI Vulnerability Research Team for responsibly reporting the identified issue.

### Impact Kirby's [blocks field](https://getkirby.com/docs/reference/panel/fields/blocks) stores structured data for each block. This data is then used in [block snippets](https://getkirby.com/docs/reference/panel/fields/blocks#block-snippets) to convert the blocks to HTML for use in your templates. We recommend to [escape HTML special characters](https://getkirby.com/docs/guide/templates/escaping) against cross-site scripting (XSS) attacks. Cross-site scripting (XSS) is a type of vulnerability that allows to execute any kind of JavaScript code inside the site frontend or Panel session of other users. If the user is logged in to the Panel, a harmful script can for example trigger requests to Kirby's API with the permissions of the victim. The default snippet for the [image block](https://getkirby.com/docs/reference/panel/blocks/image) unfortunately did not use our escaping helper. This made it possible to include malicious HTML code in the source, alt and link fields of the image block, which would then be displayed on the site frontend and executed in the browsers of site visitors and logged in users who are browsing the site. This vulnerability is critical if you might have potential attackers in your group of authenticated Panel users. They can escalate their privileges if they get access to the Panel session of an admin user. Depending on your site, other JavaScript-powered attacks are possible. You are *not* affected if you don't use the blocks field or specifically the image block in any of your blueprints. You are also protected if you use a custom [block snippet](https://getkirby.com/docs/reference/panel/fields/blocks#block-snippets) that either escapes the printed values or doesn't use them. The attack can only be performed by logged-in users and only surfaces in the site frontend (i.e. in your templates). The Panel itself is unaffected and will not execute JavaScript that was injected into the image block content. ### Patches We have patched the vulnerability in [Kirby 3.5.8](https://github.com/getkirby/kirby/releases/tag/3.5.8) by escaping special HTML characters in the output from the default image block snippet. Please update to this or a [later version](https://github.com/getkirby/kirby/releases/) to fix the vulnerability. ### Credits Thanks to Azrul Ikhwan Zulkifli (@azrultech) from BAE Systems AI Vulnerability Research Team for responsibly reporting the identified issue.

Kirby es un CMS estructurado de archivos de código abierto. En las versiones afectadas, el campo blocks de Kirby almacena datos estructurados para cada bloque. Estos datos son usados en los fragmentos de bloque para convertir los bloques a HTML para ser usados en sus plantillas. Recomendamos escapar los caracteres especiales de HTML para protegerse de los ataques de tipo cross-site scripting (XSS). Lamentablemente, el fragmento predeterminado para el bloque de imágenes no usaba nuestro ayudante de escape. Esto permitía incluir código HTML malicioso en los campos source, alt y link del bloque de imagen, que luego se mostraría en el frontend del sitio y se ejecutaría en los navegadores de los visitantes del sitio y de los usuarios registrados que estuvieran navegando por él. Los atacantes deben estar en su grupo de usuarios autenticados del Panel para poder explotar esta debilidad. Los usuarios que no hacen uso del campo blocks no están afectados. Este problema ha sido parcheado en la versión 3.5.8 de Kirby al escapar los caracteres HTML especiales en la salida del fragmento de bloque de imagen por defecto. Por favor, actualice a esta versión o a una posterior para corregir la vulnerabilidad