viksoe GMail Drive shell extension allows remote attackers to perform virtual filesystem actions via e-mail messages with certain subject lines, as demonstrated by (1) a GMAILFS: [13;a;1] message with a new filename and a file attachment, which injects a new file into the filesystem; (2) a GMAILFS: [13;a;1] message with an existing filename and a file attachment, which overwrites existing file content; and (3) a GMAILFS: [14;a;1] message, which creates a folder.