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Slash Open Source Project

Slash: Updated Slash Repo on

posted by pudge on 02:01 PM October 1st, 2009   Printer-friendly   Email story

The public Slash repo has not been updated in awhile. We've moved to git and long story short, it took us some time to make it available. We hope to update the public repo weekly. It is available on, and there's basic instructions available for getting started with the git repo.

The old CVS repo will remain there, but for now, it is ... old. So don't use it unless you want to look at ancient history.

There's no plans for any tarballs or official releases. If this is of value to you, I suggest you consider doing your own releases of it. Talk to me about it if you're interested in moving forward.

Slash: Two Slash Data Sanitization Security Issues

posted by jamiemccarthy on 10:15 AM June 16th, 2008   Printer-friendly   Email story

Two longstanding security issues were found and fixed in Slash, the code that powers Slashdot, in May 2008. The second of the two -- found and reported to us by Scott R. White, of -- is easily exploitable and must be fixed immediately on all Slash 2.x sites.

The first, found and fixed on May 1, was a problem with filtering certain types of form data: form inputs where the form name is matched against a regex. At some point years ago, during refactoring, the code was changed to use a named variable, instead of the default variable, so the matching was not actually being done, and the corresponding values were not being properly sanitized.

No known exploits -- either for the database, or cross-site scripting (XSS) -- exist for this issue, but though a code review was performed and a way was not found to abuse it, that doesn't mean it couldn't be abused.

The second issue, found and fixed on May 23, is similar: the code to properly filter the "sid" of a story was not anchored properly, and additional data could be tacked onto the value and left unsanitized. We thank Scott R. White for alerting us to the problem in a responsible manner.

As with the above issue, no known database exploits exist for this issue, however it is easily exploitable with standard XSS techniques, and all Slash sites must either update to the latest code, or use the patch at the link above to manually fix their site.

Both issues have existed for years. If you are on Slash 2.x, you are almost certainly affected.

As always (not that this happens often!), please contact us about security matters at, and join the low-traffic slashcode-general mailing list to keep updated on security-related matters. This security warning has been posted to that list.

Slash: Full disclosure on Friday's security issue, and new patch

posted by jamiemccarthy on 06:25 PM January 7th, 2008   Printer-friendly   Email story

On Friday, January 4, 2008, a serious security vulnerability was discovered, and an exploit demonstrated, in the then-current version of Slash. The vulnerability was an SQL injection. Its effect was to allow a user with no special authorization to read any information from any table the Slash site's mysql user was authorized to read (which may include other databases, including information_schema).

This vulnerability has been present in Slash for years. We are not going to list which specific versions of Slash are vulnerable, because as far as we know, they all are. Fortunately for those of you who are not running near-current CVS, the patch is easy to apply to all versions of Slash.

The Slash programming team would like to thank blackybr, of the Russian web-security portal site, for bringing this to our attention in a responsible manner.

The ability of an attacker to read the users table is why we urged Slash sites on Friday to change their admins' passwords. Whether the threat rises to the level of requiring all your users to change their passwords, we leave up to site administrators. Mitigating factors include:

  • We are not aware of this attack actually having been used. Of course, since we are providing full information today, every Slash site administrator should assume that attackers are now actively trying to penetrate your site using this information.
  • Passwords are MD5'd in the users table, so an attacker does not learn them directly. (It is of course likely that one or more of your users has an MD5 that shows up in a dictionary hash table, and/or than an attacker can brute-force the hashes offline.)
  • If your site is running MySQL 4.0 or earlier, we do not know of any way that significant data could be retrieved. SQL injections on MySQL do not allow for multiple queries in the default configuration, so the way to retrieve data is to inject an ANDed subquery into a WHERE clause known to be true and see whether the expected data is successfully returned. This tells the attacker one bit of information, for example, whether ASCII(SUBSTRING((SELECT x FROM y WHERE z), 1, 1)) > 90. Absent subqueries, which were added in MySQL 4.1, only data from the main query's table can be retrieved. In this case, the only known exploitable table is journals, from which not much interesting can be learned.
  • As far as we know, numerous requests in this fashion are required to obtain each byte of data. On the order of 100 requests are needed to obtain a user password. You may be able to scan your site's web logs to see if you can locate multiple suspicious-looking requests, especially to The word "select" in a query string would be a giveaway.

One of the first things that an attacker would likely do is to obtain an administrator's password. Since Slash keeps permanent records of all administrator accesses, you may wish to scan that log for unexpected and possibly unauthorized logins. For example:

mysql> SELECT uid, host_addr, MIN(ts), MAX(ts), COUNT(*) FROM accesslog_admin WHERE ts >= '2007-12-01 00:00:00' GROUP BY uid, host_addr;

Today, I have committed two more fields in the $form hashref to be run through filter_params. They are content_type, for which I could find no vulnerabilities, and userfield, for which a XSS vulnerability (less serious than blackybr's) was found. We therefore again urge Slash site administrators to either update to the latest version in CVS, or to manually add those two fields to the alphanumeric $form field filtering done in, as follows:

diff -U3 -r1.224 -r1.225
--- Slash/Utility/Environment/	4 Jan 2008 19:14:07 -0000	1.224
+++ Slash/Utility/Environment/	7 Jan 2008 21:30:09 -0000	1.225
@@ -1856,8 +1856,8 @@

 	# fields that have ONLY a-zA-Z0-9_
 	my %alphas = map {($_ => 1)} qw(
-		fieldname formkey commentstatus filter
-		hcanswer mode op section thisname type reskey
+		content_type fieldname formkey commentstatus filter
+		hcanswer mode op section thisname type reskey userfield
 	# Survey

Again, this is in addition to the patch mentioned on Friday, which added id.

As a personal note: none of us who work on Slash are very pleased with this, of course. The last time we made this kind of announcment was just over three years ago, which, while long, is not long enough.

We regret the oversight, and we will be taking additional steps in the coming weeks to make similar types of vulnerability both less likely and less serious. Please feel free to post any questions on this story, or to email me (Jamie McCarthy) with private concerns at To notify us of additional security issues we may not be aware of, please email If you are a Slash site administrator, please subscribe to slashcode-general (it's low-traffic). Thank you.

Security: add 'id' to filter_params

posted by jamiemccarthy on 03:00 PM January 4th, 2008   Printer-friendly   Email story

Whatever version of Slash you are running, please add 'id' to the list of numeric filtered parameters. This list can be found in the filter_params subroutine in If you are on near-current code, you can just update to current code, as the fix is in CVS. If not, here is the (extremely simple) diff:

diff -U3 -r1.223 -r1.224
--- Slash/Utility/Environment/	24 Oct 2007 21:19:34 -0000	1.223
+++ Slash/Utility/Environment/	4 Jan 2008 19:14:07 -0000	1.224
@@ -1823,7 +1823,7 @@

 	# fields that are numeric only
 	my %nums = map {($_ => 1)} qw(
-		approved artcount art_offset bseclev
+		approved artcount art_offset bseclev id
 		buymore cid clbig clsmall cm_offset
 		commentlimit commentsort commentspill
 		del displaystatus limit

You should also change the passwords for all your admin user accounts.

We are working on a more complete writeup of this issue, and we will append it to this story on Monday morning, Jan. 7. Please check back then. This message is also being sent to our slashcode-general mailing list (which all Slash site administrators should be reading).

Monday Update: Please see today's story with more information and a new (also small) patch.

Slash: Update DST Table for 2007

posted by pudge on 07:09 PM December 1st, 2006   Printer-friendly   Email story
Because of a change in U.S. law in 2005 (and in Canada, where most provinces have followed suit), DST is now a few weeks longer. Which means Slash needs a small update. Here's the SQL line to run (and it will be added to the sql/upgrades file next week).

REPLACE INTO dst (region, selectable, start_hour, start_wnum, start_wday, start_month, end_hour, end_wnum, end_wday, end_month) VALUES ('America', 1, 2,  2, 0, 2, 2,  1, 0, 10);

Don't forget to run it before DST starts again, at 2 a.m. on the second Sunday in March (March 11 this coming year).

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