fix(sanitizer): non-allowed attributes are not properly stripped

Regression introduced in commit 58178d90cb

internal/reader/sanitizer/sanitizer.go

@@ -127,9 +127,11 @@ func Sanitize(baseURL, input string) string {
 				attrNames, htmlAttributes := sanitizeAttributes(baseURL, tagName, token.Attr)
 				if hasRequiredAttributes(tagName, attrNames) {
 					if len(attrNames) > 0 {
+						// Rewrite the start tag with allowed attributes.
 						buffer.WriteString("<" + tagName + " " + htmlAttributes + ">")
 					} else {
-						buffer.WriteString(token.String())
+						// Rewrite the start tag without any attributes.
+						buffer.WriteString("<" + tagName + ">")
 					}
 
 					tagStack = append(tagStack, tagName)
@@ -138,7 +140,7 @@ func Sanitize(baseURL, input string) string {
 		case html.EndTagToken:
 			if len(blockedStack) == 0 {
 				if isValidTag(tagName) && slices.Contains(tagStack, tagName) {
-					buffer.WriteString(token.String())
+					buffer.WriteString("</" + tagName + ">")
 				}
 			} else {
 				if blockedStack[len(blockedStack)-1] == tagName {
@@ -155,7 +157,7 @@ func Sanitize(baseURL, input string) string {
 					if len(attrNames) > 0 {
 						buffer.WriteString("<" + tagName + " " + htmlAttributes + "/>")
 					} else {
-						buffer.WriteString(token.String())
+						buffer.WriteString("<" + tagName + "/>")
 					}
 				}
 			}

internal/reader/sanitizer/sanitizer_test.go

@@ -685,3 +685,13 @@ func TestHiddenParagraph(t *testing.T) {
 		t.Errorf(`Wrong output: "%s" != "%s"`, expected, output)
 	}
 }
+
+func TestAttributesAreStripped(t *testing.T) {
+	input := `<p style="color: red;">Some text.<hr style="color: blue"/>Test.</p>`
+	expected := `<p>Some text.<hr/>Test.</p>`
+
+	output := Sanitize("http://example.org/", input)
+	if expected != output {
+		t.Errorf(`Wrong output: "%s" != "%s"`, expected, output)
+	}
+}