Copy Post: preserve backslashes in duplicated post content

[shsajalchowdhury]

What was the problem?

When duplicating a post via the Copy Post feature, backslash characters (\) were stripped from the post content. For example, \t is a tab in a code block became t is a tab.

This happened because wp_update_post() calls wp_unslash() on array input (via wp_insert_post() → sanitize_post()), but the source data from get_post() is already unslashed. The double unslashing removes legitimate backslash characters.

Closes #46020

How was it fixed?

Added wp_slash() to the data array before passing it to wp_update_post(). This way, wp_unslash() inside wp_update_post() restores the original content with backslashes intact.

This matches the documented behavior in WordPress core: wp_update_post() only auto-slashes when passed an object, not an array. When passing an array, the caller is responsible for slashing the data.

Reference: https://developer.wordpress.org/reference/functions/wp_update_post/

Changes

• projects/plugins/jetpack/modules/copy-post.php — wrap $data in wp_slash() before wp_update_post()
• projects/plugins/jetpack/tests/php/modules/copy-post/Copy_Post_Test.php — added tests for backslash preservation
• projects/plugins/jetpack/changelog/fix-copy-post-backslash-stripping — changelog entry

Testing instructions

• Create a post with a Code block containing \t is a tab
• Save the post
• From the post list, click "Duplicate" (Jetpack Copy Post)
• Open the duplicated post
• Verify the backslash is preserved: \t is a tab (not t is a tab)
• Also test with content containing \\, \n, \f to confirm all are preserved
• Run existing tests: jetpack test php --filter=copy-post

Does this pull request change what data or activity we track or use?

No. This PR only fixes how post content is passed to a WordPress core function. No data collection, tracking, or privacy-related changes.

[github-actions]

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[tbradsha]

Somehow this PR slipped through the cracks and a separate fix was merged (#48870), so I'll close this one, but thanks for your contribution!