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:
References
Impact
When processing theming resources (i.e.
*.lessfiles) 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
.lessfiles.This is an example of inline JavaScript in a Less file:
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:
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:
References