Arbitrary file writes via crafted deep links

Path traversal in Basecamp for Android before 4.2.1 allows attackers to write files in the app's private directory via a crafted intent. The deep-link handler uses attacker-controlled path data for a private-directory file operation without preventing traversal and permits the response target to resolve to another app. Exploitation requires a malicious Android intent, and the bounded consequences are app-private file writes or disclosure of server responses to another app.