Fatal error when `wxr_cdata()` is called with non-string value #10595

hbhalodia · 2025-12-04T11:51:00Z

Add soft type safe check to wxr_cdata function, and typecast the incoming input to string.

Trac ticket: https://core.trac.wordpress.org/ticket/64347

This Pull Request is for code review only. Please keep all other discussion in the Trac ticket. Do not merge this Pull Request. See GitHub Pull Requests for Code Review in the Core Handbook for more details.

github-actions · 2025-12-04T11:51:11Z

The following accounts have interacted with this PR and/or linked issues. I will continue to update these lists as activity occurs. You can also manually ask me to refresh this list by adding the props-bot label.

Core Committers: Use this line as a base for the props when committing in SVN:

Props hbhalodia, westonruter.

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github-actions · 2025-12-04T12:07:23Z

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src/wp-admin/includes/export.php

westonruter · 2025-12-17T23:40:16Z

src/wp-admin/includes/export.php

+		if ( ! is_string( $str ) ) {
+			return '';
+		}


I believe I may be contradicting a previous suggestion I had here, but here's the latest informed by my latest research:

Suggested change

if ( ! is_string( $str ) ) {

return '';

}

if ( ! is_string( $str ) && is_scalar( $str ) ) {

$str = (string) $str;

}

Or:

Suggested change

if ( ! is_string( $str ) ) {

return '';

}

$str = (string) $str;

Hi @westonruter, I guess the first suggestion should be something like below,

if ( ! is_string( $str ) || is_scalar( $str ) ) { $str = (string) $str; }

This is because, what if data is null? ! is_string( null ) would evaluate to true, but is_scalar( null ) would evaluate to false, hence $str will remain as is and would not change to string, it would then gives the fatal for null value.

https://www.php.net/manual/en/function.is-scalar.php#:~:text=(PHP%204%20%3E=%204.0.,consider%20NULL%20to%20be%20scalar.

I would like to go by casting it to str whatever value it is as per - https://core.trac.wordpress.org/ticket/64347#comment:14

Oh, interesting. I wasn't aware that is_scalar( null ) is false. That's news to me and counter-intuitive.

westonruter · 2025-12-24T06:29:57Z

tests/phpunit/tests/admin/exportWp.php

+		$wpdb->update(
+			$wpdb->posts,
+			array(
+				'post_excerpt' => null,


The post_excerpt field actually cannot be null:

wordpress-develop/src/wp-admin/includes/schema.php

Line 166 in 63e679c

post_excerpt text NOT NULL,

Therefore, this test doesn't test a null value here. I'll remove this test.

Thanks, but I have added that the usecase that even setting null would automatically convert to string, which will pass anyhow we add null or not.

Well, I tried running these tests against trunk without the fix applied, and this test didn't error, which means that null wasn't passed to wxr_cdata().

westonruter · 2025-12-24T06:31:02Z

tests/phpunit/tests/admin/exportWp.php

+		$wpdb->update(
+			$wpdb->users,
+			array(
+				'display_name' => null,


The display_name cannot be null:

wordpress-develop/src/wp-admin/includes/schema.php

Line 202 in 63e679c

display_name varchar(250) NOT NULL default '',

So this isn't actually passing a null value to wxr_cdata(). I'll remove this test.

westonruter

This looks good to me.

Review from Gemini:

The changes look solid and address the reported fatal error by explicitly casting the input to wxr_cdata() to a string, which satisfies the strict type requirement of wp_is_valid_utf8(). The added test cases cover posts, comments, and term meta, ensuring the fix works across different content types that might contain NULL meta values.

Here is a review of the changes:

`src/wp-admin/includes/export.php`

wxr_cdata():
- The explicit cast $str = (string) $str; correctly handles NULL values by converting them to an empty string, preventing the TypeError in wp_is_valid_utf8().
- The DocBlock update to @param string|null $str accurately reflects that the function can now safely accept (and expects) null values from the database.

`tests/phpunit/tests/admin/exportWp.php`

New Tests:
- test_export_with_null_postmeta_values(): Correctly reproduces the issue by using $wpdb->insert() to bypass potentially strict sanitization in add_post_meta() that might otherwise cast NULL before insertion.
- test_export_with_null_comment_values() and test_export_with_null_term_meta_values(): Appropriately cover the other metadata tables.
- The assertions assertNotFalse( $xml ) and the check for channel->item count are sufficient to verify the export process completed without a fatal error.

General

Coding Standards: The code adheres to WordPress coding standards (spacing, indentation, casting).
Safety: The fix is backward compatible with the behavior of seems_utf8() (which was used previously) regarding NULL values, restoring functionality for exports containing NULL meta.

I have no requested changes. The patch is ready for commit.

…ng passed value to `string`. This ensures that `wp_is_valid_utf8()` does not cause a type error since it only accepts strings. Developed in #10595 Follow-up to [60630]. Props hbhalodia, westonruter, desrosj, albigdd, jorbin. See #38044. Fixes #64347. git-svn-id: https://develop.svn.wordpress.org/trunk@61405 602fd350-edb4-49c9-b593-d223f7449a82

github-actions · 2025-12-24T06:47:15Z

A commit was made that fixes the Trac ticket referenced in the description of this pull request.

SVN changeset: 61405
GitHub commit: 814279b

This PR will be closed, but please confirm the accuracy of this and reopen if there is more work to be done.

…ng passed value to `string`. This ensures that `wp_is_valid_utf8()` does not cause a type error since it only accepts strings. Developed in WordPress/wordpress-develop#10595 Follow-up to [60630]. Props hbhalodia, westonruter, desrosj, albigdd, jorbin. See #38044. Fixes #64347. Built from https://develop.svn.wordpress.org/trunk@61405 git-svn-id: http://core.svn.wordpress.org/trunk@60717 1a063a9b-81f0-0310-95a4-ce76da25c4cd

…ng passed value to `string`. This ensures that `wp_is_valid_utf8()` does not cause a type error since it only accepts strings. Developed in WordPress/wordpress-develop#10595 Follow-up to [60630]. Props hbhalodia, westonruter, desrosj, albigdd, jorbin. See #38044. Fixes #64347. Built from https://develop.svn.wordpress.org/trunk@61405 git-svn-id: https://core.svn.wordpress.org/trunk@60717 1a063a9b-81f0-0310-95a4-ce76da25c4cd

Typecast the input param to string for typesaftey and fix fatal

ee4170b

westonruter reviewed Dec 5, 2025

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src/wp-admin/includes/export.php Show resolved Hide resolved

Early return if the incoming data is not a string

ca33f76

hbhalodia requested a review from westonruter December 5, 2025 04:54

westonruter reviewed Dec 17, 2025

View reviewed changes

hbhalodia added 3 commits December 23, 2025 15:30

Add unit test and update function to typecast directly to string

28a1642

Merge branch 'trunk' into fix/issue-64347

1935b18

Revert unintended change

ae9cf2a

hbhalodia requested a review from westonruter December 23, 2025 10:05

hbhalodia and others added 6 commits December 23, 2025 15:37

Fix phpcs fixes

ec6d04e

Fix phpcbf issues

f13e834

Merge branch 'trunk' into fix/issue-64347

d3c09aa

Remove since tags from tests

5d3398c

Document that null may be passed to wxr_cdata() in practice

3feaf8b

Remove tests which do not cover issue

f146384

westonruter reviewed Dec 24, 2025

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westonruter approved these changes Dec 24, 2025

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github-actions bot closed this Dec 24, 2025

Fatal error when wxr_cdata() is called with non-string value #10595

Fatal error when wxr_cdata() is called with non-string value #10595

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src/wp-admin/includes/export.php

tests/phpunit/tests/admin/exportWp.php

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github-actions bot commented Dec 24, 2025

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Fatal error when `wxr_cdata()` is called with non-string value #10595

Fatal error when `wxr_cdata()` is called with non-string value #10595

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`src/wp-admin/includes/export.php`

`tests/phpunit/tests/admin/exportWp.php`