People are increasingly using “secure messaging apps”—communications apps which completely, or partly, use end-to-end encryption—to share information, engage with one another, and conduct commerce. Such malicious effects may be patterns that nudge users to share personal information or forward messages to insecure channels, suggestive user interfaces or flawed security mechanisms that can compromise security, or design features that encourage the propagation of mis- and disinformation or enable harassment and abuse. If you have expertise or experience that is relevant to this investigation, (such as cryptography, secure app development, UI work, or work with at-risk communities relying on secure messaging apps) or are aware of other relevant efforts, we hope to hear from you.