CVE-2021-21316

less-openui5 is an npm package which enables building OpenUI5 themes with Less.js. In less-openui5 before version 0.10., when processing theming resources (i.e. *.less files) with less-openui5 that originate from an untrusted source, those resources might contain JavaScript code which will be executed in the context of the build process. While this is a feature of the Less.js library it is an unexpected behavior in the context of OpenUI5 and SAPUI5 development. Especially in the context of UI5 Tooling which relies on less-openui5. An attacker might create a library or theme-library containing a custom control or theme, hiding malicious JavaScript code in one of the .less files. Refer to the referenced GHSA-3crj-w4f5-gwh4 for examples. Starting with Less.js version 3.0.0, the Inline JavaScript feature is disabled by default. less-openui5 however currently uses a fork of Less.js v1.6.3. Note that disabling the Inline JavaScript feature in Less.js versions 1.x, still evaluates code has additional double codes around it. We decided to remove the inline JavaScript evaluation feature completely from the code of our Less.js fork. This fix is available in less-openui5 version 0.10.0.

less-openui5 is an npm package which enables building OpenUI5 themes with Less.js. In less-openui5 before version 0.10., when processing theming resources (i.e. *.less files) with less-openui5 that originate from an untrusted source, those resources might contain JavaScript code which will be executed in the context of the build process. While this is a feature of the Less.js library it is an unexpected behavior in the context of OpenUI5 and SAPUI5 development. Especially in the context of UI5 Tooling which relies on less-openui5. An attacker might create a library or theme-library containing a custom control or theme, hiding malicious JavaScript code in one of the .less files. Refer to the referenced GHSA-3crj-w4f5-gwh4 for examples. Starting with Less.js version 3.0.0, the Inline JavaScript feature is disabled by default. less-openui5 however currently uses a fork of Less.js v1.6.3. Note that disabling the Inline JavaScript feature in Less.js versions 1.x, still evaluates code has additional double codes around it. We decided to remove the inline JavaScript evaluation feature completely from the code of our Less.js fork. This fix is available in less-openui5 version 0.10.0.

Impact

When processing theming resources (i.e. *.less files) with less-openui5 that originate from an untrusted source, those resources might contain JavaScript code which will be executed in the context of the build process.

While this is a feature of the Less.js library, it is an unexpected behavior in the context of OpenUI5 and SAPUI5 development.

Especially in the context of UI5 Tooling, which relies on less-openui5, this poses a security threat:

An attacker might create a library or theme-library containing a custom control or theme, hiding malicious JavaScript code in one of the .less files.

This is an example of inline JavaScript in a Less file:

.rule {
	@var: `(function(){console.log('Hello from JavaScript'); process.exit(1);})()`;
	color: @var;
}

Starting with Less.js version 3.0.0, the Inline JavaScript feature is disabled by default. less-openui5 however currently uses a fork of Less.js v1.6.3.

Note that disabling the Inline JavaScript feature in Less.js versions 1.x, still evaluates code has additional double codes around it:

.rule {
	@var: "`(function(){console.log('Hello from JavaScript'); process.exit(1);})()`";
	color: @var;
}

Patches

We decided to remove the inline JavaScript evaluation feature completely from the code of our Less.js fork.

This fix is available in less-openui5 version v0.10.0

Workarounds

Only process trusted theming resources.

For more information

If you have any questions or comments about this advisory:

• Open an issue in https://github.com/SAP/less-openui5
• Email us at [email protected]

less-openui5 is an npm package which enables building OpenUI5 themes with Less.js. In less-openui5 before version 0.10., when processing theming resources (i.e. *.less files) with less-openui5 that originate from an untrusted source, those resources might contain JavaScript code which will be executed in the context of the build process. While this is a feature of the Less.js library it is an unexpected behavior in the context of OpenUI5 and SAPUI5 development. Especially in the context of UI5 Tooling which relies on less-openui5. An attacker might create a library or theme-library containing a custom control or theme, hiding malicious JavaScript code in one of the .less files. Refer to the referenced GHSA-3crj-w4f5-gwh4 for examples. Starting with Less.js version 3.0.0, the Inline JavaScript feature is disabled by default. less-openui5 however currently uses a fork of Less.js v1.6.3. Note that disabling the Inline JavaScript feature in Less.js versions 1.x, still evaluates code has additional double codes around it. We decided to remove the inline JavaScript evaluation feature completely from the code of our Less.js fork. This fix is available in less-openui5 version 0.10.0.

less-openui5 is an npm package which enables building OpenUI5 themes with Less.js. In less-openui5 before version 0.10., when processing theming resources (i.e. *.less files) with less-openui5 that originate from an untrusted source, those resources might contain JavaScript code which will be executed in the context of the build process. While this is a feature of the Less.js library it is an unexpected behavior in the context of OpenUI5 and SAPUI5 development. Especially in the context of UI5 Tooling which relies on less-openui5. An attacker might create a library or theme-library containing a custom control or theme, hiding malicious JavaScript code in one of the .less files. Refer to the referenced GHSA-3crj-w4f5-gwh4 for examples. Starting with Less.js version 3.0.0, the Inline JavaScript feature is disabled by default. less-openui5 however currently uses a fork of Less.js v1.6.3. Note that disabling the Inline JavaScript feature in Less.js versions 1.x, still evaluates code has additional double codes around it. We decided to remove the inline JavaScript evaluation feature completely from the code of our Less.js fork. This fix is available in less-openui5 version 0.10.0.

Impact

When processing theming resources (i.e. *.less files) with less-openui5 that originate from an untrusted source, those resources might contain JavaScript code which will be executed in the context of the build process.

While this is a feature of the Less.js library, it is an unexpected behavior in the context of OpenUI5 and SAPUI5 development.

Especially in the context of UI5 Tooling, which relies on less-openui5, this poses a security threat:

An attacker might create a library or theme-library containing a custom control or theme, hiding malicious JavaScript code in one of the .less files.

This is an example of inline JavaScript in a Less file:

.rule {
	@var: `(function(){console.log('Hello from JavaScript'); process.exit(1);})()`;
	color: @var;
}

Starting with Less.js version 3.0.0, the Inline JavaScript feature is disabled by default. less-openui5 however currently uses a fork of Less.js v1.6.3.

Note that disabling the Inline JavaScript feature in Less.js versions 1.x, still evaluates code has additional double codes around it:

.rule {
	@var: "`(function(){console.log('Hello from JavaScript'); process.exit(1);})()`";
	color: @var;
}

Patches

We decided to remove the inline JavaScript evaluation feature completely from the code of our Less.js fork.

This fix is available in less-openui5 version v0.10.0

Workarounds

Only process trusted theming resources.

For more information

If you have any questions or comments about this advisory:

• Open an issue in https://github.com/SAP/less-openui5
• Email us at [email protected]