Fix malformed ActivityPub handles for email-based logins

[obenland]

Fixes #2070.

Proposed changes:

• Modified get_preferred_username() method in includes/model/class-user.php to detect email-based logins and sanitize them using sanitize_title()
• Added comprehensive test coverage in tests/includes/model/class-test-user.php to verify proper email username sanitization
• Ensures ActivityPub handles are properly formatted as @[email protected] instead of malformed @[email protected]@domain.com

Other information:

• Have you written new tests for your changes, if applicable?

Testing instructions:

Setup

1. Install and activate the ActivityPub plugin in a WordPress test environment
2. Install and configure Site Kit with Google authentication (or manually create a user with email-based login)

Test Case 1: Email-based Login from Site Kit

1. Create a test user via Site Kit Google login, which typically creates a username like [email protected]
2. Navigate to the user's ActivityPub profile page or use the webfinger endpoint
3. Expected result: ActivityPub handle should be @[email protected]
4. Previous buggy behavior: Handle was malformed as @[email protected]@yourdomain.com

Test Case 2: Manual Email-based Username

1. Create a user with login name [email protected]
2. Check their ActivityPub handle via webfinger or profile
3. Expected result: Handle should be @[email protected]

Test Case 3: Normal Username (Regression Test)

1. Create a user with normal login name normaluser
2. Check their ActivityPub handle
3. Expected result: Handle should be @[email protected] (unchanged behavior)

Test Case 4: Run Unit Tests

npm run env-test -- --filter=test_email_username_sanitization

Expected result: All tests should pass

Changelog entry

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Changelog Entry Details

Significance

• Patch

Type

• Fixed - for any bug fixes

Message

Fix malformed ActivityPub handles for users with email-based logins (e.g., from Site Kit Google authentication)

[Copilot]

Pull Request Overview

This PR fixes malformed ActivityPub handles for users with email-based login names, such as those created through Site Kit Google authentication. The issue occurred when usernames containing "@" symbols resulted in double "@" symbols in ActivityPub handles.

• Modified get_preferred_username() to sanitize email-based usernames using sanitize_title()
• Added comprehensive test coverage to verify proper email username sanitization
• Ensures ActivityPub handles are properly formatted without malformed double "@" symbols

Reviewed Changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
includes/model/class-user.php	Modified get_preferred_username() to detect and sanitize email-based login names
tests/includes/model/class-test-user.php	Added comprehensive test cases for email username sanitization scenarios

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[Jiwoon-Kim]

If the administrator creates a new account using a Google email address but sets the username in a non-email format (a regular ID instead of an email), and then links it via Sign in with Google, this bug can be bypassed.

Honestly, I’m not entirely sure whether this should be debugged on the ActivityPub side, or if it’s something that Site Kit should address by changing how it handles email-based username creation.

If my memory serves me correctly, Misskey prevents users from creating accounts with email-style IDs at signup (or at least explicitly instructs users not to enter them).

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However, since the author page ID for email-based accounts does not include special characters, this fix still seems to have some value.

[Jiwoon-Kim]

The profile URL is generated as:
https://travel-in-busan.com/author/kimjiwoon75gmail-com/

To maintain consistency with the ActivityPub handle, instead of replacing @ with a hyphen, the @ should be omitted entirely.

👉 Desired format:
@[email protected]

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is not very “clean” as a username.

It may be worth considering a redirect mechanism in the future so that such legacy usernames can point to a cleaner, newly chosen identifier.

Of course, this would also require solving the name collision problem (e.g., if two users try to adopt the same “cleaned” username).

👉 In practice, this would mean:

Keep the legacy handle for backwards compatibility.

Allow the user/admin to register a new canonical handle.

Set up a redirect/alias system so that old mentions and followers still resolve correctly.

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This should be addressed together with the ability for users to edit their blog profile handle. For example, mechanisms that allow arbitrary manipulation of the handle—such as using the posts page slug as the handle—should be prevented. The goal is to maintain consistency and integrity of ActivityPub handles across posts and profiles.