Fix regression of special comments

docs/changelog.md

@@ -10,6 +10,12 @@ and this project adheres to the
 [Python Version Specification](https://packaging.python.org/en/latest/specifications/version-specifiers/).
 See the [Contributing Guide](contributing.md) for details.
 
+## [Unreleased]
+
+### Fixed
+
+* Fix a regression related to comment handling (#1590).
+
 ## [3.10.1] - 2026-01-21
 
 ### Fixed

markdown/htmlparser.py

@@ -276,7 +276,7 @@ def handle_entityref(self, name: str):
 
     def handle_comment(self, data: str):
         # Check if the comment is unclosed, if so, we need to override position
-        j = len(self.rawdata) - len(data)
+        j = self.rawdata.find(data)
         i = j - 2
         if self.rawdata[i:j] == '</':
             self.handle_data('<')

tests/test_syntax/blocks/test_html_blocks.py

@@ -1706,3 +1706,29 @@ def test_no_hang_issue_1586(self):
             'Test `<!--[if mso]>` and `<!--[if !mso]>`',
             '<p>Test <code>&lt;!--[if mso]&gt;</code> and <code>&lt;!--[if !mso]&gt;</code></p>'
         )
+
+    def test_issue_1590(self):
+        """Test case with comments in table for issue #1590."""
+
+        self.assertMarkdownRenders(
+            self.dedent(
+                '''
+                <table>
+                <!--[if mso]>-->
+                <td>foo</td>
+                <!--<!endif]-->
+                <td>bar</td>
+                </table>
+                '''
+            ),
+            self.dedent(
+                '''
+                <table>
+                <!--[if mso]>-->
+                <td>foo</td>
+                <!--<!endif]-->
+                <td>bar</td>
+                </table>
+                '''
+            )
+        )