CVE-2025-21088 WebApp crash via improper validation of proto style in attachments

Mattermost versions 10.2.x = 10.2.0, 9.11.x = 9.11.5, 10.0.x = 10.0.3, 10.1.x = 10.1.3 fail to properly validate the style of proto supplied to an action's style in post.props.attachments, which allows an attacker to crash the frontend via crafted malicious input...