diff --git a/Doxyfile b/Doxyfile
index 6c5b301a..9089d3be 100644
--- a/Doxyfile
+++ b/Doxyfile
@@ -31,7 +31,7 @@ PROJECT_NAME           = HTMLPurifier
 # This could be handy for archiving the generated documentation or
 # if some version control system is used.
 
-PROJECT_NUMBER         = 4.17.0
+PROJECT_NUMBER         = 4.18.0
 
 # The OUTPUT_DIRECTORY tag is used to specify the (relative or absolute)
 # base path where the generated documentation will be put.
diff --git a/NEWS b/NEWS
index 2ed3cabe..f4d3040c 100644
--- a/NEWS
+++ b/NEWS
@@ -1,3 +1,23 @@
+# [4.18.0](https://github.com/ezyang/htmlpurifier/compare/v4.17.0...v4.18.0) (2024-11-01)
+
+
+### Bug Fixes
+
+* Adjust Core.AllowHostnameUnderscore to consider that "_" is defined as Unreserved Characters in RFC 3986 ([#406](https://github.com/ezyang/htmlpurifier/issues/406)) ([d9fbef8](https://github.com/ezyang/htmlpurifier/commit/d9fbef8e27f6a0848a8987a8534351de98eb0fa1))
+* Avoid a deprecated error when the attribute name is numeric and DirectLex is used ([#412](https://github.com/ezyang/htmlpurifier/issues/412)) ([f0fbf51](https://github.com/ezyang/htmlpurifier/commit/f0fbf510981b27fc03168efdb17d6bff48f521af))
+* checking that node has property name ([#399](https://github.com/ezyang/htmlpurifier/issues/399)) ([9ca5a36](https://github.com/ezyang/htmlpurifier/commit/9ca5a3687bd2e6e42ed9d5199b2cfb1dbd6dbdc2))
+* Ignore conditional comments ([#401](https://github.com/ezyang/htmlpurifier/issues/401)) ([4828fdf](https://github.com/ezyang/htmlpurifier/commit/4828fdf45a93eeeacfcbcc855f96f9a7e6b4ed44))
+* Support PHP 8.4 ([#396](https://github.com/ezyang/htmlpurifier/issues/396)) ([92da247](https://github.com/ezyang/htmlpurifier/commit/92da2473ffbb3ed5e894560d4166b1ca8032aeb3))
+* undefined array key warning ([#419](https://github.com/ezyang/htmlpurifier/issues/419)) ([01be377](https://github.com/ezyang/htmlpurifier/commit/01be377f93654fad4d3fbc8c81779f14316eaecf))
+
+
+### Features
+
+* Add allowfullscreen attr for iframe ([#411](https://github.com/ezyang/htmlpurifier/issues/411)) ([70754a2](https://github.com/ezyang/htmlpurifier/commit/70754a253342f67a67425cfa81029db3a5c1bd28))
+* add directive for removing blank nodes ([#404](https://github.com/ezyang/htmlpurifier/issues/404)) ([c9d60c9](https://github.com/ezyang/htmlpurifier/commit/c9d60c96d799c02bc357c88a49f422034b6914fd))
+* Add support for CSS aspect-ratio ([#408](https://github.com/ezyang/htmlpurifier/issues/408)) ([93bee73](https://github.com/ezyang/htmlpurifier/commit/93bee733497a098b65daf5910f1c435d347860a4))
+* Allow universal CSS values for all properties ([#410](https://github.com/ezyang/htmlpurifier/issues/410)) ([9723267](https://github.com/ezyang/htmlpurifier/commit/972326785d201b81e1095bc296b99bbcfa8c7fd4))
+
 # [4.17.0](https://github.com/ezyang/htmlpurifier/compare/v4.16.0...v4.17.0) (2023-11-17)
 
 
diff --git a/VERSION b/VERSION
index 8643e722..ef8ffbdd 100644
--- a/VERSION
+++ b/VERSION
@@ -1 +1 @@
-4.17.0
\ No newline at end of file
+4.18.0
\ No newline at end of file
diff --git a/configdoc/usage.xml b/configdoc/usage.xml
index fd1a8a54..05ff285f 100644
--- a/configdoc/usage.xml
+++ b/configdoc/usage.xml
@@ -6,7 +6,7 @@
   </file>
   <file name="HTMLPurifier/Lexer.php">
    <line>90</line>
-   <line>331</line>
+   <line>315</line>
   </file>
   <file name="HTMLPurifier/Lexer/DirectLex.php">
    <line>67</line>
@@ -19,37 +19,37 @@
  </directive>
  <directive id="CSS.MaxImgLength">
   <file name="HTMLPurifier/CSSDefinition.php">
-   <line>256</line>
+   <line>253</line>
   </file>
  </directive>
  <directive id="CSS.Proprietary">
   <file name="HTMLPurifier/CSSDefinition.php">
-   <line>398</line>
+   <line>397</line>
   </file>
  </directive>
  <directive id="CSS.AllowTricky">
   <file name="HTMLPurifier/CSSDefinition.php">
-   <line>402</line>
+   <line>401</line>
   </file>
  </directive>
  <directive id="CSS.Trusted">
   <file name="HTMLPurifier/CSSDefinition.php">
-   <line>406</line>
+   <line>405</line>
   </file>
  </directive>
  <directive id="CSS.AllowImportant">
   <file name="HTMLPurifier/CSSDefinition.php">
-   <line>410</line>
+   <line>409</line>
   </file>
  </directive>
  <directive id="CSS.AllowedProperties">
   <file name="HTMLPurifier/CSSDefinition.php">
-   <line>539</line>
+   <line>538</line>
   </file>
  </directive>
  <directive id="CSS.ForbiddenProperties">
   <file name="HTMLPurifier/CSSDefinition.php">
-   <line>555</line>
+   <line>554</line>
   </file>
  </directive>
  <directive id="Cache.DefinitionImpl">
@@ -124,7 +124,7 @@
    <line>122</line>
   </file>
   <file name="HTMLPurifier/Lexer.php">
-   <line>313</line>
+   <line>299</line>
   </file>
  </directive>
  <directive id="Output.Newline">
@@ -172,12 +172,15 @@
    <line>234</line>
   </file>
   <file name="HTMLPurifier/Lexer.php">
-   <line>318</line>
-   <line>358</line>
+   <line>304</line>
+   <line>342</line>
   </file>
   <file name="HTMLPurifier/AttrDef/HTML/ContentEditable.php">
    <line>8</line>
   </file>
+  <file name="HTMLPurifier/HTMLModule/Iframe.php">
+   <line>43</line>
+  </file>
   <file name="HTMLPurifier/HTMLModule/Image.php">
    <line>37</line>
   </file>
@@ -267,22 +270,22 @@
  <directive id="Core.LegacyEntityDecoder">
   <file name="HTMLPurifier/Lexer.php">
    <line>220</line>
-   <line>342</line>
+   <line>326</line>
   </file>
  </directive>
  <directive id="Core.ConvertDocumentToFragment">
   <file name="HTMLPurifier/Lexer.php">
-   <line>329</line>
+   <line>313</line>
   </file>
  </directive>
  <directive id="Core.RemoveProcessingInstructions">
   <file name="HTMLPurifier/Lexer.php">
-   <line>352</line>
+   <line>336</line>
   </file>
  </directive>
  <directive id="Core.HiddenElements">
   <file name="HTMLPurifier/Lexer.php">
-   <line>356</line>
+   <line>340</line>
   </file>
   <file name="HTMLPurifier/Strategy/RemoveForeignElements.php">
    <line>36</line>
@@ -290,12 +293,12 @@
  </directive>
  <directive id="Core.AggressivelyRemoveScript">
   <file name="HTMLPurifier/Lexer.php">
-   <line>357</line>
+   <line>341</line>
   </file>
  </directive>
  <directive id="Core.RemoveScriptContents">
   <file name="HTMLPurifier/Lexer.php">
-   <line>358</line>
+   <line>342</line>
   </file>
   <file name="HTMLPurifier/Strategy/RemoveForeignElements.php">
    <line>35</line>
@@ -408,12 +411,12 @@
  </directive>
  <directive id="Core.AllowHostnameUnderscore">
   <file name="HTMLPurifier/AttrDef/URI/Host.php">
-   <line>77</line>
+   <line>71</line>
   </file>
  </directive>
  <directive id="Core.EnableIDNA">
   <file name="HTMLPurifier/AttrDef/URI/Host.php">
-   <line>109</line>
+   <line>103</line>
   </file>
  </directive>
  <directive id="Attr.DefaultTextDir">
@@ -470,17 +473,17 @@
  </directive>
  <directive id="Filter.ExtractStyleBlocks.TidyImpl">
   <file name="HTMLPurifier/Filter/ExtractStyleBlocks.php">
-   <line>94</line>
+   <line>106</line>
   </file>
  </directive>
  <directive id="Filter.ExtractStyleBlocks.Scope">
   <file name="HTMLPurifier/Filter/ExtractStyleBlocks.php">
-   <line>125</line>
+   <line>137</line>
   </file>
  </directive>
  <directive id="Filter.ExtractStyleBlocks.Escaping">
   <file name="HTMLPurifier/Filter/ExtractStyleBlocks.php">
-   <line>334</line>
+   <line>351</line>
   </file>
  </directive>
  <directive id="HTML.Forms">
@@ -552,6 +555,11 @@
    <line>72</line>
   </file>
  </directive>
+ <directive id="Core.RemoveBlanks">
+  <file name="HTMLPurifier/Lexer/DOMLex.php">
+   <line>75</line>
+  </file>
+ </directive>
  <directive id="Core.DirectLexLineNumberSyncInterval">
   <file name="HTMLPurifier/Lexer/DirectLex.php">
    <line>84</line>
diff --git a/library/HTMLPurifier.includes.php b/library/HTMLPurifier.includes.php
index 77ebf2de..4c713a33 100644
--- a/library/HTMLPurifier.includes.php
+++ b/library/HTMLPurifier.includes.php
@@ -7,7 +7,7 @@
  * primary concern and you are using an opcode cache. PLEASE DO NOT EDIT THIS
  * FILE, changes will be overwritten the next time the script is run.
  *
- * @version 4.17.0
+ * @version 4.18.0
  *
  * @warning
  *      You must *not* include any other HTML Purifier files before this file,
@@ -101,6 +101,7 @@ require 'HTMLPurifier/AttrDef/CSS/Length.php';
 require 'HTMLPurifier/AttrDef/CSS/ListStyle.php';
 require 'HTMLPurifier/AttrDef/CSS/Multiple.php';
 require 'HTMLPurifier/AttrDef/CSS/Percentage.php';
+require 'HTMLPurifier/AttrDef/CSS/Ratio.php';
 require 'HTMLPurifier/AttrDef/CSS/TextDecoration.php';
 require 'HTMLPurifier/AttrDef/CSS/URI.php';
 require 'HTMLPurifier/AttrDef/HTML/Bool.php';
diff --git a/library/HTMLPurifier.php b/library/HTMLPurifier.php
index 5c14a335..e3bca8a2 100644
--- a/library/HTMLPurifier.php
+++ b/library/HTMLPurifier.php
@@ -19,7 +19,7 @@
  */
 
 /*
-    HTML Purifier 4.17.0 - Standards Compliant HTML Filtering
+    HTML Purifier 4.18.0 - Standards Compliant HTML Filtering
     Copyright (C) 2006-2008 Edward Z. Yang
 
     This library is free software; you can redistribute it and/or
@@ -58,12 +58,12 @@ class HTMLPurifier
      * Version of HTML Purifier.
      * @type string
      */
-    public $version = '4.17.0';
+    public $version = '4.18.0';
 
     /**
      * Constant with version of HTML Purifier.
      */
-    const VERSION = '4.17.0';
+    const VERSION = '4.18.0';
 
     /**
      * Global configuration object.
diff --git a/library/HTMLPurifier.safe-includes.php b/library/HTMLPurifier.safe-includes.php
index 94543f59..8a417d24 100644
--- a/library/HTMLPurifier.safe-includes.php
+++ b/library/HTMLPurifier.safe-includes.php
@@ -95,6 +95,7 @@ require_once $__dir . '/HTMLPurifier/AttrDef/CSS/Length.php';
 require_once $__dir . '/HTMLPurifier/AttrDef/CSS/ListStyle.php';
 require_once $__dir . '/HTMLPurifier/AttrDef/CSS/Multiple.php';
 require_once $__dir . '/HTMLPurifier/AttrDef/CSS/Percentage.php';
+require_once $__dir . '/HTMLPurifier/AttrDef/CSS/Ratio.php';
 require_once $__dir . '/HTMLPurifier/AttrDef/CSS/TextDecoration.php';
 require_once $__dir . '/HTMLPurifier/AttrDef/CSS/URI.php';
 require_once $__dir . '/HTMLPurifier/AttrDef/HTML/Bool.php';
diff --git a/library/HTMLPurifier/Config.php b/library/HTMLPurifier/Config.php
index f7511ca4..e6566e80 100644
--- a/library/HTMLPurifier/Config.php
+++ b/library/HTMLPurifier/Config.php
@@ -21,7 +21,7 @@ class HTMLPurifier_Config
      * HTML Purifier's version
      * @type string
      */
-    public $version = '4.17.0';
+    public $version = '4.18.0';
 
     /**
      * Whether or not to automatically finalize