Cross-site Scripting (XSS) possible due to improper sanitisation of `href` attributes on `<a>` tags
### Summary
There is a potential cross-site scripting (XSS) vulnerability that can be exploited via maliciously crafted user data.
Our filter to detect and prevent the use of the `javascript:` URL scheme in the `href` attribute of an `<a>` tag could be bypassed with tab `\t` or newline `\n` characters between the characters of the protocol, e.g. `java\tscript:`.
### Impact
If you render an `<a>` tag with an `href` attribute set to a user-provided link, that link could potentially execute JavaScript when clicked by another user.
```ruby
a(href: user_profile) { "Profile" }
```
### Mitigation
The best way to mitigate this vulnerability is to update to one of the following versions:
- 1.10.1
https://rubygems.org/gems/phlex/versions/1.10.1
- 1.9.2
https://rubygems.org/gems/phlex/versions/1.9.2
- 1.8.3
https://rubygems.org/gems/phlex/versions/1.8.3
- 1.7.2
https://rubygems.org/gems/phlex/versions/1.7.2
- 1.6.3
https://rubygems.org/gems/phlex/versions/1.6.3
- 1.5.3
https://rubygems.org/gems/phlex/versions/1.5.3
- 1.4.2
https://rubygems.org/gems/phlex/versions/1.4.2
### Workarounds
Configuring a Content Security Policy
https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Content-Security-Policy that does not allow `unsafe-inline`
https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Content-Security-Policy#unsafe-inline would effectively prevent this vulnerability from being exploited.