personnummer/csharp vulnerable to Improper Input Validation

Summary

This vulnerability was reported to the personnummer team in June 2020. The slow response was due to locked ownership of some of the affected packages, which caused delays to update packages prior to disclosure.

The vulnerability is determined to be low severity.

### Impact

This vulnerability impacts users who rely on the for last digits of personnummer to be a _real_ personnummer.

### Patches

The issue have been patched in all repositories. The following versions should be updated to as soon as possible:

[C#](https://github.com/advisories/GHSA-qv8q-v995-72gr) 3.0.2 D 3.0.1 [Dart](https://github.com/advisories/GHSA-4xh4-v2pq-jvhm) 3.0.3 Elixir 3.0.0 [Go](https://github.com/advisories/GHSA-hv53-vf5m-8q94) 3.0.1 [Java](https://github.com/advisories/GHSA-q3vw-4jx3-rrr2) 3.3.0 [JavaScript](https://github.com/advisories/GHSA-vpgc-7h78-gx8f) 3.1.0 Kotlin 1.1.0 Lua 3.0.1 [PHP](https://github.com/advisories/GHSA-2p6g-gjp8-ggg9) 3.0.2 Perl 3.0.0 [Python](https://github.com/advisories/GHSA-rxq3-5249-8hgg) 3.0.2 [Ruby](https://github.com/advisories/GHSA-vp9c-fpxx-744v) 3.0.1 [Rust](https://github.com/advisories/GHSA-28r9-pq4c-wp3c) 3.0.0 Scala 3.0.1 Swift 1.0.1

If you are using any of the earlier packages, please update to latest.

### Workarounds

The issue arrieses from the regular expression allowing the first three digits in the last four digits of the personnummer to be 000, which is invalid. To mitigate this without upgrading, a check on the last four digits can be made to make sure it's not 000x.

### For more information

If you have any questions or comments about this advisory: * Open an issue in [Personnummer Meta](https://github.com/personnummer/meta/issues) * Email us at [Personnummer Email](mailto:security@personnummer.dev)