Directory traversal vulnerability in the installer in PEAR 1.0 through 1.5.3 allows user-assisted remote attackers to overwrite arbitrary files via a .. (dot dot) sequence in the (1) install-as attribute in the file element in package.xml 1.0 or the (2) as attribute in the install element in package.xml 2.0.  NOTE: it could be argued that this does not cross privilege boundaries in typical installations, since the code being installed could perform the same actions.