build(deps): bump github.com/microcosm-cc/bluemonday from 1.0.2 to 1.0.16 in /example

[dependabot[bot]]

Bumps github.com/microcosm-cc/bluemonday from 1.0.2 to 1.0.16.

Release notes

Sourced from github.com/microcosm-cc/bluemonday's releases.

Prevent a HTML sanitization vulnerability

CVE-2021-42576

A vulnerability was discovered by https://github.com/TomAnthony https://www.tomanthony.co.uk/ which allowed the contents of a style tag to be leaked unsanitized by bluemonday into the HTML output. Further it was demonstrated that if the form elements select and option were allowed by the policy that this could result in a successful XSS.

You would only be vulnerable to if if you allowed style, select and option in your HTML sanitization policy:

p := bluemonday.NewPolicy()
p.AllowElements("style","select")
html := p.Sanitize(`<select><option><style><script>alert(1)</script>`)
fmt.Println(html)

bluemonday very strongly recommends not allowing the style element in a policy. It is fundamentally unsafe as we do not have a CSS sanitizer and the content is passed through unmodified.

bluemonday has been updated to explicitly suppress style and script elements by default even if you do allow them by policy as these are considered unsafe. If you have a use-case for using bluemonday whilst trusting the input then you can assert this via p.AllowUnsafe(true) which will let style and script through if the policy also allows them.

Note: the policies shipped with bluemonday are not vulnerable to this.

Fix XSS vulnerability in HTML attribute parsing

A well crafted HTML attribute had the potential to evade sanitization due to incorrect escaping of the attribute whilst serializing it.

This version resolves that issue. In doing so it will also correctly use & to separate query string values in URLs within HTML attributes (href, src, ...).

Add SanitizeReaderToWriter(r io.Reader, w io.Writer)

No release notes provided.

Policies that accept regexps for matching are now additive

Thanks to @​KN4CK3R for the contribution of a PR that results in multiple Matching() policies on the same attr and element no longer clobber the previous regexps.

Improve data-uri base64 handling, and improve docs structure

No release notes provided.

Improve support for links on all elements

Originally I had only concentrated the link validation on the elements that were safe to link. However people do want to allow some unsafe elements and yet still have the benefits of link validation and sanitization, i.e. allow iframe but still have the src safely validated... these changes allow that.

Additionally I have added tests showing how AllowSchemesWithCustomPolicy can be used to globally allow only links to certain domains, and a test that shows how to apply the AllowAttributes().Matching().OnElements to only allow a given domain on specific elements (i.e. only allow an iframe if is is a YouTube embed).

AllowComments

Adds a new func to allow HTML comments to be allowed. But does not allow CDATA comments which will be treated as plain HTML comments.

Also updates the readme, and the versions of the dependencies that have also updated.

Update x/net to latest version

As per https://nvd.nist.gov/vuln/detail/CVE-2020-28852

Restore support for go < 1.10

No release notes provided.

... (truncated)

Commits

• c788a2a Prevent a HTML sanitization vulnerability
• 13d1799 go fmt with go 1.17
• cada0f0 Merge pull request #128 from 6543-forks/ci-enforce-code-format
• 7e9370a CI.restart()
• be04ac9 enforce "lf" line ending
• 9926455 Add "Check Code Formation" step to CI
• 1b5510c add "fmt-check" make target
• 1a86fcd go mod tidy && go fmt
• f0057e2 Fix escaping of HTML attributes
• c0a6f20 Spelling mistakes and whitespace are OK
• Additional commits viewable in compare view

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