The Web Application Hacker’s Handbook Discovering and Exploiting Security Flaws

If you find a path traversal vulnerability that grants write access, your

main goal should be to exploit this to achieve arbitrary execution of com-

mands on the server. Means of exploiting the vulnerability to achieve this

include:

■

Creating scripts in users’ startup folders.

■

Modifying files such as 

in.ftpd

to execute arbitrary commands when

a user next connects.

■

Writing scripts to a web directory with execute permissions and calling

them from your browser.

Preventing Path Traversal Vulnerabilities

By far the most effective means of eliminating path traversal vulnerabilities is

to avoid passing user-submitted data to any file system API. In many cases,

including the original example 

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, it is