ffcss is a CLI interface to apply and configure Firefox CSS themes. Prior to 0.2.0, the function `lookupPreprocess()` is meant to apply some transformations to a string by disabling characters in the regex `[-_ .]`. However, due to the use of late Unicode normalization of type NFKD, it is possible to bypass that validation and re-introduce all the characters in the regex `[-_ .]`. The `lookupPreprocess()` can be easily bypassed with equivalent Unicode characters like U+FE4D (﹍), which would result in the omitted U+005F (_), for instance. The `lookupPreprocess()` function is only ever used to search for themes loosely (case insensitively, while ignoring dashes, underscores and dots), so the actual security impact is classified as low. This vulnerability is fixed in 0.2.0. There are no known workarounds.
The product constructs all or part of a command, data structure, or record using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify how it is parsed or interpreted when it is sent to a downstream component.
| Link | Tags |
|---|---|
| https://github.com/ewen-lbh/ffcss/security/advisories/GHSA-wpmx-564x-h2mh | vendor advisory exploit |
| https://github.com/ewen-lbh/ffcss/commit/f9c491874b858a32fcae15045f169fd7d02f90dc | patch |