Notice in redirect_guess_404_permalink() when post type is an array

[junaidbhura]

When manipulating URLs, it sometimes becomes necessary to update the query using the pre_get_posts hook.

If we set the post type to an array in the pre_get_posts hook like so:

$query->set( 'post_type', array( 'post', 'page', 'my_cpt' ) );

On a 404 page, we get a notice when WP_DEBUG is set to true:

Notice: wpdb::prepare was called incorrectly. The query only expected one placeholder, but an array of multiple placeholders was sent.

This is caused by the following code in redirect_guess_404_permalink():

$where .= $wpdb->prepare(" AND post_type = %s", get_query_var('post_type'));

This can be fixed by looking for an array and updating the query.

[pento]

I suspect 43056.diff​ will introduce SQL injection issues. wpdb:prepare() won't put quotes around each element of the array being sent to it when replacing into the %s.

[Enchiridion]

This issue has been bugging me too. I've updated the patch with SQL escaping.

[laternastudio]

Would love to see this released soon!

[Enchiridion]

Small optimization added

[peterwilsoncc]

I've taken a look at 43056.2.diff​

The escaping looks good with esc_url, the post types are verified as legitimate in class-wp.php.

You'll notice that at the moment, the canonical guess function uses get_query_var( 'post_type' ) calls multiple times. This is to act as a safety switch so that the value of a variable isn't changed by mistake -- this can lead to problems ;)

Rather than putting the value in a variable, I think calling get_query_var( 'post_type' ) each time would an improvement.

[junaidbhura]

Nice catch @peterwilsoncc ! I've updated and attached a new diff, could you please take a look?

Trac ticket: https://core.trac.wordpress.org/ticket/43056

[peterwilsoncc]

@junaidbhura I've modified your patch slightly in ​PR 480 on the GitHub repo:

• The escaping was a little out, $wpdb->prepare() can't be used for IN so the query would have being incorrect, it would have looked for a post type of an apparently random concatenation of the post types. I've replaced that with the counter-intuitive method of correctly escaping LIKEs.
• I've added some unit tests too for array formatted post types. I've used the publicly queryable post types in a query string rather than the pre_get_posts filter example in your initial report.

[junaidbhura]

Thanks @peterwilsoncc ! I've added a couple of comments on your PR. Could you please take a look?

[peterwilsoncc]

43056.4.diff​ is the final state of the PR with tests and @junaidbhura's code

[peterwilsoncc]

In 49200:

Canonical: Support multiple post types in redirect_guess_404_permalink().

Prevent redirect_guess_404_permalink() from throwing a notice when multiple post types are included in the post_type query.

Props junaidbhura.
Fixes #43056.

Merged into WP Core in https://core.trac.wordpress.org/changeset/49200

[junaidbhura]

Sweet thanks @peterwilsoncc !