[drupal-devel] [bug] XSS vulnerability in comments

[Mogurito]

Issue status update for 
http://drupal.org/node/31197
Post a follow up: 
http://drupal.org/project/comments/add/31197

 Project:      Drupal
 Version:      4.6.0
 Component:    comment.module
 Category:     bug reports
 Priority:     critical
 Assigned to:  Mogurito
 Reported by:  Mogurito
 Updated by:   Mogurito
 Status:       patch (code needs review)

*CORRECTION* (The comment is not complete)


The source code interpreted by the browser, have html comment with the
subject by each comment. For example, if we post a comment like
'Hello', Drupal write in the source code . But the problem come when a
post is send with special characters like '<'. If we post a comment
like '-->Hello XSS', the comment in the source code will be closed,
provocating that "Hello XSS-->" string will be show in the page. If the
"Hello XSS" string will be replaced by a script, we can get a XSS
Attack.


Solution
Analize the subject string and replacing the special characters (<,>,
') for (&<, &>, &")


How
Adding this lines to the function comment_validate_form:
$edit['subject'] = ereg_replace("<", "&<", $edit['subject']);
$edit['subject'] = ereg_replace(">", "&>", $edit['subject']);
$edit['subject'] = ereg_replace(""", "&"", $edit['subject']);


Notes
- Sorry, but my english is not very cool.




Mogurito



Previous comments:
------------------------------------------------------------------------

Wed, 14 Sep 2005 12:12:05 +0000 : Mogurito

Attachment: http://drupal.org/files/issues/comment.module_13.diff (632 bytes)

The source code interpreted by the browser, have html comment with the
subject by each comment. For example, if we post a comment like
'Hello', Drupal write in the source code . But the problem come when a
post is send with special characters like 'Hello XSS', the comment in
the source code will be closed, provocating that "Hello XSS-->" string
will be show in the page. If the "Hello XSS" string will be replaced by
a script, we can get a XSS Attack.


*Solution*
Analize the subject string and replacing the special characters (, ')
for (<, >, ")


*How*
Adding this lines to the function comment_validate_form:
$edit['subject'] = ereg_replace("", ">", $edit['subject']);
$edit['subject'] = ereg_replace("\'", """, $edit['subject']);


*Notes*
- Sorry, but my english is not very cool.