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Opened 8 years ago

Closed 8 years ago

Last modified 8 years ago

#3973 closed defect (bug) (fixed)

XSRF,XSS security hole for users with unfiltered_html capability

Reported by: markjaquith Owned by: markjaquith
Milestone: 2.0.10 Priority: highest omg bbq
Severity: critical Version: 2.1.2
Component: Security Keywords: comment nonce form security XSS XSRF
Focuses: Cc:

Description

As reported at:

http://www.virtuax.be/advisories/Advisory4-20022007.txt

Users with the unfiltered_html capability get to skip KSES stripping of harmful HTML markup. An XSRF attack can be used to trick these users into submitting comments with harmful XSS-laden markup.

Attached patch is a first stab at a solution for trunk, 2.0.x and 2.1.x

The patch alters wp_nonce_field() so that the form name can be specified. For users with unfiltered_html the comment_form hook is used to use wp_nonce_field to inject a hidden nonced field, using a special name.

On comment submit, users with unfiltered_html have this nonce checked. If the nonce check fails, KSES silently reverts to normal non-unfiltered_html operation, zapping any XSS-esque content and rendering the attack useless. This silent fallback is used so that themes without the comment_form hook don't block unfiltered_html-capable comments... they just sanitize them more closely than they would if the theme supported the comment_form hook.

Triple milestone: 2.2 (trunk), 2.1.3, 2.0.10

Trunk has been tested with this patch, and 2.1.x applied cleanly. 2.0.x has not yet been tested.

Attachments (1)

unfiltered_html_xsrf_xss.diff (8.7 KB) - added by markjaquith 8 years ago.
Patch for all three WP branches

Download all attachments as: .zip

Change History (7)

@markjaquith8 years ago

Patch for all three WP branches

comment:1 @ryan8 years ago

Code looks good.

comment:2 @markjaquith8 years ago

  • Resolution set to fixed
  • Status changed from new to closed

(In [5039]) nonce-protect comments by users with unfiltered_html cap to prevent xsrf/xss. fixes #3973 for trunk

comment:3 @markjaquith8 years ago

(In [5040]) nonce-protect comments by users with unfiltered_html cap to prevent xsrf/xss. fixes #3973 for 2.1

comment:4 @markjaquith8 years ago

(In [5041]) nonce-protect comments by users with unfiltered_html cap to prevent xsrf/xss. fixes #3973 for 2.0

comment:5 @technosailor8 years ago

Reviewing per Ryan on Twitter. (the new mode of communication)... :-)

Looks good here too.

comment:6 @charleshooper8 years ago

(off topic) Ah, gotta love twitter

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