A local file inclusion/path traversal vulnerability and XSS flaw was found in the Mantis bug tracker version 1.2.7 ,.
Created mantis tracking bugs for this issue
Affects: fedora-all [bug 731854]
Affects: epel-5 [bug 731855]
Version 1.2.8 has been released:
Also upgrading the severity based on the author's following comments:
I don't think my earlier message conveyed the severity of this bug well
MantisBT allows users to upload attachments to bug reports. These
attachments are commonly stored on the disk in an 'attachments'
directory that should be stored outside the web root (but are still
accessible to MantisBT for retrieval).
This LFI vulnerbility therefore allows arbitrary remote code execution
on a target server (as the web user ID). This level of access could be
used to connect to the MantisBT database and access files and
configuration of other web applications operating under the same uid/gid
as the MantisBT installation.
For example, this LFI vulnerability may allow an attacker to call:
Note that as per the earlier notice, some users (such as those using
nginx) may not be impacted at all.
Starting the update process.
However, I need to note the impact of the flaw is not as severe for those using the default settings, that is, storing attachments in the database.
CVE assignments for flaws fixed in 1.2.8 are as follows:
CVE-2011-3356: XSS injection via PHP_SELF ,
CVE-2011-3357: LFI and XSS via bug_actiongroup_ext_page.php 
CVE-2011-3358: XSS issues with unescaped os, os_build and platform parameters on bug_report_page.php and bug_update_advanced_page.php 
Another CVE assignment was made:
Common Vulnerabilities and Exposures assigned an identifier CVE-2011-3578 to
the following vulnerability:
Cross-site scripting (XSS) vulnerability in
bug_actiongroup_ext_page.php in MantisBT before 1.2.8 allows remote
attackers to inject arbitrary web script or HTML via the action
parameter, related to bug_actiongroup_page.php, a different
vulnerability than CVE-2011-3357.
Currently supported Fedora versions have 1.2.8, which include the fix. EPEL5's 1.1.8 may yet be affected by (or a subset of) these issues.
EPEL5 hasn't been touched since Dec 2010, and the package is technically orphaned. As a result I'm closing this bug as this issue is fixed in Fedora. The EPEL5 tracking bug #800667 will remain open until either mantis is dropped from EPEL or it is fixed.