buildForwardContent copied content.file (AES key/iv/hashes) verbatim, so forwarding from an E2EE room into an unencrypted one published the key. For unencrypted destinations the attachment is now downloaded, decrypted and re-uploaded as plaintext (url instead of file, thumbnail key stripped); if that fails the forward is refused rather than leaking. Encrypted destinations unchanged. Needs a manual check on a live encrypted -> plaintext forward. Fixes #63 Co-Authored-By: Claude Opus 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01PPmy3tPq869XDW4njjVaKA