The bug is an information-disclosure logic error in WebKit’s Now Playing integration. When a media element or Web Audio context plays audio, WebCore computes a NowPlayingInfo structure (title, artist, album, artwork, unique identifier) and hands it to the platform so the media can be surfaced in system UI such as Control Center, the lock screen, and the Now Playing widget.

The invariant that was violated is that content playing inside a private-browsing (ephemeral) session must never leak identifying metadata to persistent, system-visible surfaces, and that metadata must not be published while media playback for the page is suspended. Before the patch, HTMLMediaElement::isNowPlayingEligible() unconditionally returned m_mediaSession->hasNowPlayingInfo() and MediaElementSession::computeNowPlayingInfo() / AudioContext::nowPlayingInfo() built and returned the full info record without consulting the page’s session type, so a private tab’s media title (which can reveal the visited site or content) was exposed through the system Now Playing interface.

The fix adds explicit ephemeral-session and suspension gates: AudioContext::isNowPlayingEligible() now returns false when there is no document or when page->mediaPlaybackIsSuspended(); AudioContext::nowPlayingInfo() returns an empty/placeholder record early when page->usesEphemeralSession(); HTMLMediaElement gains an out-of-line isNowPlayingEligible() that also returns false when playback is suspended; and MediaElementSession::computeNowPlayingInfo() null-checks the page and, for an ephemeral session, blanks title/artist/album/artwork before returning. These changes restore the invariant that ephemeral browsing produces no persistent, cross-context-visible Now Playing metadata. This is purely a policy/logic fix; nothing in the diff touches memory management, so there is no memory-corruption primitive here — the harm is confined to leaking private-session information to the local system UI.

This is an information-disclosure/privacy bug, not a memory-safety primitive: the diff contains no allocation, lifetime, or bounds logic that could be turned toward OOB/UAF, and there is no path to memory corruption or code execution from it. The concrete harm is that private-browsing media metadata (a title that can reveal the visited site or content) leaks to persistent, system-level Now Playing surfaces that are readable without authenticating the device (e.g. at the lock screen). It executes in and leaks from the WebContent process’s media pipeline into the platform’s shared Now Playing state; severity is medium precisely because it is a confidentiality leak rather than an exploitation chain.