Fix escaped document tags in code being taken for the document's own

CHANGELOG.md

@@ -8,6 +8,7 @@ Updates should follow the [Keep a CHANGELOG](http://keepachangelog.com/) princip
 
 - Fixed a line of only `=` or `-` after a line break not being escaped, which made a heading out of the line before it, such as in `<p>Foo<br>=</p>` (#226). Lines of `-` were already escaped inside of paragraphs, but not inside of list items, blockquotes or headings.
 - Fixed emphasis next to an empty one of the same kind losing one of its delimiters, such as `<strong> </strong><strong>hello</strong>` becoming ` hello**` (#252). Emphasis next to one of the same kind which is removed with `remove_nodes` also lost one.
+- Fixed `&lt;/body&gt;` or `&lt;/html&gt;` in code or comments causing the document's own closing tags to be output after it, and everything from `&lt;!DOCTYPE ` in code up to the next `>` being removed, which could be the rest of the document (#254)
 
 ## [5.2.3] - 2026-10-19
 

src/HtmlConverter.php

@@ -651,7 +651,8 @@ private function endsOnBlankLine(ElementInterface $element, ConverterInterface $
     protected function sanitize(string $markdown): string
     {
         $markdown = \html_entity_decode($markdown, ENT_QUOTES, 'UTF-8');
-        $markdown = \preg_replace('/<!DOCTYPE [^>]+>/', '', $markdown); // Strip doctype declaration
+        // Only the declaration itself, which comes first, as code could contain the same text once decoded
+        $markdown = \preg_replace('/^<!DOCTYPE [^>]+>/', '', $markdown);
         \assert($markdown !== null);
         $markdown = \trim($markdown); // Remove blank spaces at the beggining of the html
 
@@ -668,8 +669,8 @@ protected function sanitize(string $markdown): string
                     $markdown = \substr($markdown, \strlen($tag));
                 }
             } else {
-                // Closing tags
-                if (\strpos($markdown, $tag) === \strlen($markdown) - \strlen($tag)) {
+                // Closing tags, which code before them could also contain once decoded
+                if (\substr($markdown, -\strlen($tag)) === $tag) {
                     $markdown = \substr($markdown, 0, -\strlen($tag));
                 }
             }

tests/HtmlConverterTest.php

@@ -393,6 +393,22 @@ public function testCodeContainingTextWhichLooksLikeItsOwnTags(): void
         $this->assertHtmlGivesMarkdown('<p><code class="a>b">x</code></p>', '`x`');
     }
 
+    /**
+     * @see https://github.com/thephpleague/html-to-markdown/issues/254
+     */
+    public function testCodeContainingTextWhichLooksLikeDocumentTags(): void
+    {
+        $this->assertHtmlGivesMarkdown('<pre><code>&lt;/body&gt;</code></pre>', "```\n</body>\n```");
+        $this->assertHtmlGivesMarkdown('<pre><code>&lt;/html&gt;</code></pre>', "```\n</html>\n```");
+        $this->assertHtmlGivesMarkdown('<pre><code>&lt;/head&gt;&lt;/body&gt;&lt;/html&gt;</code></pre>', "```\n</head></body></html>\n```");
+        $this->assertHtmlGivesMarkdown('<pre><code>&lt;html&gt;&lt;body&gt;</code></pre>', "```\n<html><body>\n```");
+        $this->assertHtmlGivesMarkdown('<p>a <code>&lt;/body&gt;&lt;/html&gt;</code></p>', 'a `</body></html>`');
+        $this->assertHtmlGivesMarkdown('<pre><code>&lt;!DOCTYPE html&gt;</code></pre>', "```\n<!DOCTYPE html>\n```");
+        $this->assertHtmlGivesMarkdown('<!DOCTYPE html><pre><code>&lt;!DOCTYPE html&gt;&lt;/html&gt;</code></pre>', "```\n<!DOCTYPE html></html>\n```");
+        $this->assertHtmlGivesMarkdown('<p>Use <code>&lt;!DOCTYPE html</code> first.</p><p>a &gt; b</p>', "Use `<!DOCTYPE html` first.\n\na &gt; b");
+        $this->assertHtmlGivesMarkdown('<p>x</p><!-- </body> -->', "x\n\n<!-- </body> -->", ['preserve_comments' => true]);
+    }
+
     public function testNestedCode(): void
     {
         $this->assertHtmlGivesMarkdown('<pre><pre>a</pre></pre>', "```\na\n```");