From 27f69d242a40e9c500c39a9a7125475c438997c4 Mon Sep 17 00:00:00 2001
From: ECYaz <elie@theofficeweb.com>
Date: Sun, 19 Jul 2026 22:49:32 -0400
Subject: [PATCH] [ticket/17655] Do not render raw codepoint shortcodes as
 emoji

The Emoji plugin renders sequences of hexadecimal digits between colons
such as ":123c:" as emoji images of the corresponding codepoint. Such
sequences commonly appear as segments of IPv6 addresses, mangling the
address and causing failing image requests to the emoji CDN which slow
down the page for the reader.

Add a filter to the EMOJI tag that rejects these shortcodes so they
remain plain text. Emoji shortnames such as ":joy:" and Unicode emoji
are unaffected. The ":1234:" shortname is rejected as well, as it
cannot be told apart from a segment of an IPv6 address.

PHPBB-17655
---
 phpBB/phpbb/textformatter/s9e/factory.php     |  6 ++++++
 phpBB/phpbb/textformatter/s9e/parser.php      | 19 ++++++++++++++++++
 .../s9e/default_formatting_test.php           | 20 +++++++++++++++++++
 3 files changed, 45 insertions(+)

diff --git a/phpBB/phpbb/textformatter/s9e/factory.php b/phpBB/phpbb/textformatter/s9e/factory.php
index e1979a27821..30a6c94fc1d 100644
--- a/phpBB/phpbb/textformatter/s9e/factory.php
+++ b/phpBB/phpbb/textformatter/s9e/factory.php
@@ -364,6 +364,12 @@ function ($m)
 		</xsl:choose>';
 		$tag->template = '<xsl:choose><xsl:when test="$S_VIEWSMILIES">' . str_replace('class="emoji"', 'class="emoji smilies"', $tag->template) . '</xsl:when><xsl:otherwise><xsl:value-of select="."/></xsl:otherwise></xsl:choose>';
 
+		// Reject shortcodes that consist of raw codepoints in hexadecimal such as ":123c:",
+		// which commonly appear as segments of IPv6 addresses
+		$tag->filterChain
+			->append(__NAMESPACE__ . '\\parser::filter_emoji')
+			->addParameterByName('tagText');
+
 		/**
 		* Modify the s9e\TextFormatter configurator after the default settings are set
 		*
diff --git a/phpBB/phpbb/textformatter/s9e/parser.php b/phpBB/phpbb/textformatter/s9e/parser.php
index 590afc0ebcf..749e11d86cf 100644
--- a/phpBB/phpbb/textformatter/s9e/parser.php
+++ b/phpBB/phpbb/textformatter/s9e/parser.php
@@ -301,6 +301,25 @@ public function set_vars(array $vars)
 		}
 	}
 
+	/**
+	* Filter an EMOJI tag to reject shortcodes that consist of raw codepoints
+	*
+	* Sequences of hexadecimal digits between colons such as ":123c:" commonly
+	* appear as segments of IPv6 addresses and should remain plain text rather
+	* than be rendered as an emoji image
+	*
+	* @param  Tag    $tag      The EMOJI tag
+	* @param  string $tag_text Original text consumed by the tag
+	* @return void
+	*/
+	static public function filter_emoji(Tag $tag, $tag_text)
+	{
+		if (preg_match('/^:[0-3][0-9a-f]{3,4}(?:-[0-9a-f]{4,5})*:$/D', $tag_text))
+		{
+			$tag->invalidate();
+		}
+	}
+
 	/**
 	* Filter a flash object's height
 	*
diff --git a/tests/text_formatter/s9e/default_formatting_test.php b/tests/text_formatter/s9e/default_formatting_test.php
index 97b04c2fb7d..2442373a907 100644
--- a/tests/text_formatter/s9e/default_formatting_test.php
+++ b/tests/text_formatter/s9e/default_formatting_test.php
@@ -320,6 +320,26 @@ function ($container)
 					$container->get('text_formatter.renderer')->set_viewsmilies(false);
 				}
 			),
+			array(
+				// PHPBB-17655 - Segments of IPv6 addresses should not be rendered as emoji
+				'IPv6: 2a09:bac3:616e:123c::1d1:f0',
+				'IPv6: 2a09:bac3:616e:123c::1d1:f0'
+			),
+			array(
+				'IPv6: 2607:fb90:ec1d:0e17:e0c6:af94:1224:28a8',
+				'IPv6: 2607:fb90:ec1d:0e17:e0c6:af94:1224:28a8'
+			),
+			array(
+				// Raw codepoint shortcodes are rejected as they cannot be told apart
+				// from segments of IPv6 addresses
+				'Codepoints: :264d: :1f600: :1234:',
+				'Codepoints: :264d: :1f600: :1234:'
+			),
+			array(
+				// Emoji shortnames keep working
+				'Shortname: :joy:',
+				'Shortname: <img alt=":joy:" class="emoji smilies" draggable="false" src="//cdn.jsdelivr.net/gh/twitter/twemoji@latest/assets/svg/1f602.svg">'
+			),
 		);
 	}
 }