diff --git a/Libraries/LibWeb/CSS/Parser/PropertyParsing.cpp b/Libraries/LibWeb/CSS/Parser/PropertyParsing.cpp
index 896253fe0b7..935827bb5f3 100644
--- a/Libraries/LibWeb/CSS/Parser/PropertyParsing.cpp
+++ b/Libraries/LibWeb/CSS/Parser/PropertyParsing.cpp
@@ -4432,7 +4432,7 @@ RefPtr<CSSStyleValue> Parser::parse_filter_value_list_value(TokenStream<Componen
                 return FilterOperation::Blur {};
             auto blur_radius = parse_length(tokens);
             tokens.discard_whitespace();
-            if (!blur_radius.has_value())
+            if (!blur_radius.has_value() || (!blur_radius->is_calculated() && blur_radius->value().raw_value() < 0))
                 return {};
             return if_no_more_tokens_return(FilterOperation::Blur { blur_radius.value() });
         } else if (filter_token == FilterToken::DropShadow) {
@@ -4498,6 +4498,12 @@ RefPtr<CSSStyleValue> Parser::parse_filter_value_list_value(TokenStream<Componen
             if (!tokens.has_next_token())
                 return FilterOperation::Color { filter_token_to_operation(filter_token) };
             auto amount = parse_number_percentage(tokens);
+            if (amount.has_value()) {
+                if (amount->is_percentage() && amount->percentage().value() < 0)
+                    return {};
+                if (amount->is_number() && amount->number().value() < 0)
+                    return {};
+            }
             return if_no_more_tokens_return(FilterOperation::Color { filter_token_to_operation(filter_token), amount });
         }
     };
diff --git a/Tests/LibWeb/Text/expected/wpt-import/css/filter-effects/parsing/backdrop-filter-parsing-invalid.txt b/Tests/LibWeb/Text/expected/wpt-import/css/filter-effects/parsing/backdrop-filter-parsing-invalid.txt
new file mode 100644
index 00000000000..56b4a41a3f4
--- /dev/null
+++ b/Tests/LibWeb/Text/expected/wpt-import/css/filter-effects/parsing/backdrop-filter-parsing-invalid.txt
@@ -0,0 +1,30 @@
+Harness status: OK
+
+Found 25 tests
+
+25 Pass
+Pass	e.style['backdrop-filter'] = "auto" should not set the property value
+Pass	e.style['backdrop-filter'] = "none hue-rotate(0deg)" should not set the property value
+Pass	e.style['backdrop-filter'] = "blur(10)" should not set the property value
+Pass	e.style['backdrop-filter'] = "blur(-100px)" should not set the property value
+Pass	e.style['backdrop-filter'] = "brightness(-20)" should not set the property value
+Pass	e.style['backdrop-filter'] = "brightness(30px)" should not set the property value
+Pass	e.style['backdrop-filter'] = "contrast(-20)" should not set the property value
+Pass	e.style['backdrop-filter'] = "contrast(30px)" should not set the property value
+Pass	e.style['backdrop-filter'] = "drop-shadow(10 20)" should not set the property value
+Pass	e.style['backdrop-filter'] = "drop-shadow(10% 20%)" should not set the property value
+Pass	e.style['backdrop-filter'] = "drop-shadow(1px)" should not set the property value
+Pass	e.style['backdrop-filter'] = "drop-shadow(1px 2px 3px 4px)" should not set the property value
+Pass	e.style['backdrop-filter'] = "drop-shadow(rgb(4, 5, 6))" should not set the property value
+Pass	e.style['backdrop-filter'] = "drop-shadow()" should not set the property value
+Pass	e.style['backdrop-filter'] = "grayscale(-20)" should not set the property value
+Pass	e.style['backdrop-filter'] = "grayscale(30px)" should not set the property value
+Pass	e.style['backdrop-filter'] = "hue-rotate(90)" should not set the property value
+Pass	e.style['backdrop-filter'] = "invert(-20)" should not set the property value
+Pass	e.style['backdrop-filter'] = "invert(30px)" should not set the property value
+Pass	e.style['backdrop-filter'] = "opacity(-20)" should not set the property value
+Pass	e.style['backdrop-filter'] = "opacity(30px)" should not set the property value
+Pass	e.style['backdrop-filter'] = "saturate(-20)" should not set the property value
+Pass	e.style['backdrop-filter'] = "saturate(30px)" should not set the property value
+Pass	e.style['backdrop-filter'] = "sepia(-20)" should not set the property value
+Pass	e.style['backdrop-filter'] = "sepia(30px)" should not set the property value
\ No newline at end of file
diff --git a/Tests/LibWeb/Text/expected/wpt-import/css/filter-effects/parsing/filter-parsing-invalid.txt b/Tests/LibWeb/Text/expected/wpt-import/css/filter-effects/parsing/filter-parsing-invalid.txt
new file mode 100644
index 00000000000..1574292daec
--- /dev/null
+++ b/Tests/LibWeb/Text/expected/wpt-import/css/filter-effects/parsing/filter-parsing-invalid.txt
@@ -0,0 +1,30 @@
+Harness status: OK
+
+Found 25 tests
+
+25 Pass
+Pass	e.style['filter'] = "auto" should not set the property value
+Pass	e.style['filter'] = "none hue-rotate(0deg)" should not set the property value
+Pass	e.style['filter'] = "blur(10)" should not set the property value
+Pass	e.style['filter'] = "blur(-100px)" should not set the property value
+Pass	e.style['filter'] = "brightness(-20)" should not set the property value
+Pass	e.style['filter'] = "brightness(30px)" should not set the property value
+Pass	e.style['filter'] = "contrast(-20)" should not set the property value
+Pass	e.style['filter'] = "contrast(30px)" should not set the property value
+Pass	e.style['filter'] = "drop-shadow(10 20)" should not set the property value
+Pass	e.style['filter'] = "drop-shadow(10% 20%)" should not set the property value
+Pass	e.style['filter'] = "drop-shadow(1px)" should not set the property value
+Pass	e.style['filter'] = "drop-shadow(1px 2px 3px 4px)" should not set the property value
+Pass	e.style['filter'] = "drop-shadow(rgb(4, 5, 6))" should not set the property value
+Pass	e.style['filter'] = "drop-shadow()" should not set the property value
+Pass	e.style['filter'] = "grayscale(-20)" should not set the property value
+Pass	e.style['filter'] = "grayscale(30px)" should not set the property value
+Pass	e.style['filter'] = "hue-rotate(90)" should not set the property value
+Pass	e.style['filter'] = "invert(-20)" should not set the property value
+Pass	e.style['filter'] = "invert(30px)" should not set the property value
+Pass	e.style['filter'] = "opacity(-20)" should not set the property value
+Pass	e.style['filter'] = "opacity(30px)" should not set the property value
+Pass	e.style['filter'] = "saturate(-20)" should not set the property value
+Pass	e.style['filter'] = "saturate(30px)" should not set the property value
+Pass	e.style['filter'] = "sepia(-20)" should not set the property value
+Pass	e.style['filter'] = "sepia(30px)" should not set the property value
\ No newline at end of file
diff --git a/Tests/LibWeb/Text/input/wpt-import/css/filter-effects/parsing/backdrop-filter-parsing-invalid.html b/Tests/LibWeb/Text/input/wpt-import/css/filter-effects/parsing/backdrop-filter-parsing-invalid.html
new file mode 100644
index 00000000000..342680b0c98
--- /dev/null
+++ b/Tests/LibWeb/Text/input/wpt-import/css/filter-effects/parsing/backdrop-filter-parsing-invalid.html
@@ -0,0 +1,54 @@
+<!DOCTYPE html>
+<html>
+<head>
+<meta charset="utf-8">
+<title>Filter Effects Module Level 2: parsing backdrop-filter with invalid values</title>
+<link rel="author" title="Eric Willigers" href="mailto:ericwilligers@chromium.org">
+<link rel="help" href="https://drafts.fxtf.org/filter-effects-2/#BackdropFilterProperty">
+<meta name="assert" content="backdrop-filter supports only the grammar 'none | <backdrop-filter-function-list>'.">
+<script src="../../../resources/testharness.js"></script>
+<script src="../../../resources/testharnessreport.js"></script>
+<script src="../../../css/support/parsing-testcommon.js"></script>
+</head>
+<body>
+<script>
+// Edge fails: expected "" but got "none"
+
+test_invalid_value("backdrop-filter", "auto");
+test_invalid_value("backdrop-filter", "none hue-rotate(0deg)");
+
+test_invalid_value("backdrop-filter", "blur(10)");
+test_invalid_value("backdrop-filter", "blur(-100px)");
+
+test_invalid_value("backdrop-filter", "brightness(-20)");
+test_invalid_value("backdrop-filter", "brightness(30px)");
+
+test_invalid_value("backdrop-filter", "contrast(-20)");
+test_invalid_value("backdrop-filter", "contrast(30px)");
+
+test_invalid_value("backdrop-filter", "drop-shadow(10 20)");
+test_invalid_value("backdrop-filter", "drop-shadow(10% 20%)");
+test_invalid_value("backdrop-filter", "drop-shadow(1px)");
+test_invalid_value("backdrop-filter", "drop-shadow(1px 2px 3px 4px)");
+test_invalid_value("backdrop-filter", "drop-shadow(rgb(4, 5, 6))");
+test_invalid_value("backdrop-filter", "drop-shadow()");
+
+test_invalid_value("backdrop-filter", "grayscale(-20)");
+test_invalid_value("backdrop-filter", "grayscale(30px)");
+
+test_invalid_value("backdrop-filter", "hue-rotate(90)");
+
+test_invalid_value("backdrop-filter", "invert(-20)");
+test_invalid_value("backdrop-filter", "invert(30px)");
+
+test_invalid_value("backdrop-filter", "opacity(-20)");
+test_invalid_value("backdrop-filter", "opacity(30px)");
+
+test_invalid_value("backdrop-filter", "saturate(-20)");
+test_invalid_value("backdrop-filter", "saturate(30px)");
+
+test_invalid_value("backdrop-filter", "sepia(-20)");
+test_invalid_value("backdrop-filter", "sepia(30px)");
+</script>
+</body>
+</html>
diff --git a/Tests/LibWeb/Text/input/wpt-import/css/filter-effects/parsing/filter-parsing-invalid.html b/Tests/LibWeb/Text/input/wpt-import/css/filter-effects/parsing/filter-parsing-invalid.html
new file mode 100644
index 00000000000..8ab3d98dced
--- /dev/null
+++ b/Tests/LibWeb/Text/input/wpt-import/css/filter-effects/parsing/filter-parsing-invalid.html
@@ -0,0 +1,54 @@
+<!DOCTYPE html>
+<html>
+<head>
+<meta charset="utf-8">
+<title>Filter Effects Module Level 1: parsing filter with invalid values</title>
+<link rel="author" title="Eric Willigers" href="mailto:ericwilligers@chromium.org">
+<link rel="help" href="https://drafts.fxtf.org/filter-effects/#FilterProperty">
+<meta name="assert" content="filter supports only the grammar 'none | <filter-function-list>'.">
+<script src="../../../resources/testharness.js"></script>
+<script src="../../../resources/testharnessreport.js"></script>
+<script src="../../../css/support/parsing-testcommon.js"></script>
+</head>
+<body>
+<script>
+// Edge fails: expected "" but got "none"
+
+test_invalid_value("filter", "auto");
+test_invalid_value("filter", "none hue-rotate(0deg)");
+
+test_invalid_value("filter", "blur(10)");
+test_invalid_value("filter", "blur(-100px)");
+
+test_invalid_value("filter", "brightness(-20)"); // crbug.com/776208 Blink/WebKit accept negative brightness.
+test_invalid_value("filter", "brightness(30px)");
+
+test_invalid_value("filter", "contrast(-20)");
+test_invalid_value("filter", "contrast(30px)");
+
+test_invalid_value("filter", "drop-shadow(10 20)");
+test_invalid_value("filter", "drop-shadow(10% 20%)");
+test_invalid_value("filter", "drop-shadow(1px)");
+test_invalid_value("filter", "drop-shadow(1px 2px 3px 4px)");
+test_invalid_value("filter", "drop-shadow(rgb(4, 5, 6))");
+test_invalid_value("filter", "drop-shadow()");
+
+test_invalid_value("filter", "grayscale(-20)");
+test_invalid_value("filter", "grayscale(30px)");
+
+test_invalid_value("filter", "hue-rotate(90)");
+
+test_invalid_value("filter", "invert(-20)");
+test_invalid_value("filter", "invert(30px)");
+
+test_invalid_value("filter", "opacity(-20)");
+test_invalid_value("filter", "opacity(30px)");
+
+test_invalid_value("filter", "saturate(-20)");
+test_invalid_value("filter", "saturate(30px)");
+
+test_invalid_value("filter", "sepia(-20)");
+test_invalid_value("filter", "sepia(30px)");
+</script>
+</body>
+</html>