[BUG] `backdrop-filter` CSS property flagged as invalid

[yehuda100]

Describe the bug
When using the CSS property backdrop-filter in a stylesheet, the validator incorrectly flags it as non-existent:

"backdrop-filter": Property "backdrop-filter" doesn't exist.
This property is part of the standard CSS specification and is supported by all major modern browsers.

To Reproduce
Steps to reproduce the behavior:

1. Go to the CSS editor or upload a stylesheet containing backdrop-filter.
2. Use a rule like:

.btn {
  backdrop-filter: blur(10px);
}

3. Run the validation.
4. Observe the error message stating the property doesn't exist.

What is the current bug behavior

The validator incorrectly reports backdrop-filter as an invalid or unknown CSS property.

Expected behavior
The validator should recognize backdrop-filter as a valid CSS property and not flag it as an error.
It is part of the official CSS spec and widely supported across modern browsers (Chrome, Edge, Safari).

Screenshots
If applicable, include a screenshot of the error message from the validator interface.

Additional context

• The issue may stem from outdated CSS property definitions in the validator’s ruleset.
• A workaround is to use -webkit-backdrop-filter, but this should no longer be necessary.
• Reference: MDN Web Docs – backdrop-filter: https://developer.mozilla.org/en-US/docs/Web/CSS/backdrop-filter

[Cyb3r-Jak3]

My guess this is related to an old version of https://github.com/validator/validator in svenkreiss/html5validator.

[Cyb3r-Jak3]

@yehuda100 can you try with version 8.0.0?