Changed May-3-2011

Security bugs are rated by specifying [sg:<rating>] in the "Whiteboard" field in bugzilla. For example, a bug with a Critical severity rating would be marked as [sg:critical]. You might also notice a [ws:<rating>] in the "Whiteboard" field which is used for our Web Applications. The severity rating system can be found on the Web Application Security Severity Rating page.

Severity Ratings

sg:critical

Run attacker code with local user privilege or install malicious software, requiring no user interaction beyond normal browsing.

Examples:

• Overflows resulting in native code execution
• JavaScript injection into browser chrome
• Launching of arbitrary local application with provided arguments
• Filetype spoofing where executables can masquerade as benign content types
• Installation & execution of plugins/modules with chrome/native privileges, without user consent or via user dialog fatigue
• Any crash where random memory or NULL is executed (the top of the stack is not a function)
• Any crash where random memory is accessed
• Any bug where random memory is written to is critical
• Any bug where random memory is read from and then used in a subsequent memory or jump operation (offset, array, etc) is critical

sg:high

Obtain confidential data from other sites the user is visiting or the local machine, or inject data or code into those sites, requiring no more than normal browsing actions. Indefinite DoS of the user's system, requiring OS reinstallation or extensive cleanup

Examples:

• Cross-site Scripting (XSS)
• Theft of arbitrary files from local system
• Spoofing of full URL bar or bypass of SSL integrity checks
• Memory read that results in data being written into an inert container (ie string or image) that is subsequently accessible to content

sg:moderate

Disclosure of sensitive information that represents a violation of privacy but by itself does not expose the user or organization to immediate risk. The vulnerability combined with another moderate vulnerability could result in an attack of high or critical severity (aka stepping stone). Indefinite application Denial of Service (DoS) via corruption of state, requiring application re-installation or temporary DoS of the user's system, requiring reboot

Examples:

• Disclosure of OS username
• Disclosure of browser cache salt
• Disclosure of entire browsing history
• Detection of arbitrary local files
• Launching of arbitrary local application without arguments
• Local storage of passwords in unencrypted form
• Persistent DoS attacks that prevent the user from starting Firefox or another application in the future

sg:low

Minor security vulnerabilities such as leaks or spoofs of non-sensitive information.

Examples:

• Detection of previous visit to a specific site
• Identification of users by profiling browsing behavior.
• Corruption of chrome dialogs or user input without the ability to spoof arbitrary messages

sg:dos (Denial of Service)

Temporary Denial of Service attacks that users can avoid by not visiting the site again.

Note: It is not necessary to mark each bug with [sg:dos]; adding the hang or crash keyword is sufficient.

Examples:

• Script that hangs the application for more than 5-10 seconds (without triggering the "slow script" dialog)
• Application crash.
• Infinite loop of dialogs that a user cannot escape.

Mitigating Circumstances

If there are mitigating circumstances that severely reduce the effectiveness of the exploit, then the exploit could be reduced by one level of severity. Examples of mitigating circumstances include difficulty in reproducing due to very specific timing or load order requirements, complex or unusual set of actions the user would have to take beyond normal browsing behaviors, or unusual software configuration.

As a rough guide, to be considered for reduction in severity an exploit should execute successfully less than 10% of the time. If measures can be taken to improve the reliability of the exploit to over 10% (by combining it with other existing bugs or techniques), then it should not be considered to be mitigated.

Additional Security Status Codes

If a potential security issue has not yet been assigned a severity rating, or a rating is not appropriate, the whiteboard may instead contain one of the following security status codes.

Changed Oct-31-2011

Security bugs are rated by specifying [sg:<rating>] in the "Whiteboard" field in bugzilla. For example, a bug with a Critical severity rating would be marked as [sg:critical]. You might also notice a [ws:<rating>] in the "Whiteboard" field which is used for our Web Applications. The severity rating system can be found on the Web Application Security Severity Rating page.

Severity Ratings Table

Mitigating Circumstances

If there are mitigating circumstances that severely reduce the effectiveness of the exploit, then the exploit could be reduced by one level of severity. Examples of mitigating circumstances include difficulty in reproducing due to very specific timing or load order requirements, complex or unusual set of actions the user would have to take beyond normal browsing behaviors, or unusual software configuration.

As a rough guide, to be considered for reduction in severity an exploit should execute successfully less than 10% of the time. If measures can be taken to improve the reliability of the exploit to over 10% (by combining it with other existing bugs or techniques), then it should not be considered to be mitigated.

Additional Security Status Codes

If a potential security issue has not yet been assigned a severity rating, or a rating is not appropriate, the whiteboard may instead contain one of the following security status codes.