Allele Security Alert
ASA-2019-00443, CVE-2019-11730, MFSA2019-21
Same-origin policy treats all files in a directory as having the same-origin
Mozilla Firefox version before 68
Mozilla Firefox version 68
Proof of concept
A vulnerability exists where if a user opens a locally saved HTML file, this file can use file: URIs to access other files in the same directory or sub-directories if the names are known or guessed. The Fetch API can then be used to read the contents of any files stored in these directories and they may uploaded to a server. Luigi Gubello demonstrated that in combination with a popular Android messaging app, if a malicious HTML attachment is sent to a user and they opened that attachment in Firefox, due to that app’s predictable pattern for locally-saved file names, it is possible to read attachments the victim received from other correspondents.
Mozilla Foundation Security Advisory 2019-21
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Last modified: July 18, 2019