CVE 2007-2519
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.
See the 
CVE page on Mitre.org
for more details.
