A video's preview and a picture's thumbnail are made inside the request that posts the message, and
nothing bounded how long either could take.
- The video preview filter also selects any frame from 5 seconds on. Rails' filter takes the second
frame it selects, which a video with a single keyframe and no scene change only gives at its end, so
ffmpeg decoded all of it.
- TimeLimitedVideoPreviewer gives ffmpeg 10 seconds of wall-clock time, kills it past that, and reports
a failed preview, so the message is posted without one.
- Pictures and videos above 250 megapixels, or whose size couldn't be read, get no preview: decoding
costs in proportion to the pixels, however small the file.
- The view shows a preview only if it was made when the message was posted. Its URL used to make it on
view, so a preview that failed or was skipped would be attempted again on every view. The cached
presentation's version goes up, so cached messages pick this up.
- A video's poster is made, when the message is posted, at the size the view shows it. The full-size WebP
made until now wasn't shown anywhere, and encoding it costs in proportion to the frame's pixels.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Bj8KnxpTf9sj2Ysa8aLAVa
The editor keeps an attachment's content as it finds it, so a hand-written
embed with a url but no href reached the editor with its markup unvalidated,
and a mention saved under Trix's editor carried the generic octet-stream
content type the editor doesn't permit and was dropped on save. Rebuilding
each attachment from its attachable renders the hardened preview partial
and restores the mention content type.
* Bump thruster 0.1.15 → 0.1.23
* Scrub disallowed attributes on allowed tags in message rendering
SanitizeTags removes disallowed tags from message presentation, but
attributes on the tags it allows passed through untouched. Extend the
content-filter chain with a SanitizeAttributes filter that runs Rails'
safe-list sanitizer over the remaining markup, stripping event-handler
attributes and unsafe URI schemes as defense-in-depth alongside the
existing Content-Security-Policy.
Running it after SanitizeTags with the same allowed-tags list makes the
sanitizer's tag pass a no-op, preserving SanitizeTags' remove-not-unwrap
semantics while scrubbing attributes. The attribute allowlist is the
standard ActionText set (which keeps attachments intact) plus class,
which presentation styling relies on.
Marcello Costagliola
Stanko K.R.
Jeremy Daer
Kevin McConnell