[lxml-dev] Re: exslt:regexp implementation based on 're'

Martijn Faassen wrote:

One thing that I wonder about is potential security issues? Are there ways to break out of the Python regexs and call arbitrary python code? If not, then we don't need to worry about it. XSLT can be run from fairly unsafe sources so this may be a concern.

you can "hang" RE if you want (by crafting a really lousy RE that causes excessive backtracking), but since you can "hang" any XML parser that supports internal DTD:s (google for the "billion laughs attack"), I'm not sure how serious this is. I wouldn't accept XSLT programs from untrusted sources, though... </F>