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Blackboard LMS: Administrator

Safe HTML filters

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Users can enter HTML in Blackboard in a variety of ways. For example, users can enter HTML using the content editor in blogs and discussion boards, and through HTML file uploads. In the past, a security threat was introduced because users could enter potentially dangerous tags, such as script tags. Such tags could be used to execute malicious script in Blackboard, exposing other users to attacks. This is referred to as cross scripting, which allows a user to have control over other user browsers.

Safe HTML filters provide you with more control over the type of HTML students can enter, making user-supplied HTML safer to use in Blackboard. The feature replaces an earlier HTML sanitizer with the open-source security library from the Open Web Application Security Project's AntiSamy API. The new API ensures that user-supplied HTML complies with an application's rules.

Blackboard provides administrators with a default-policy.xml file containing Safe HTML rules. Administrators can define the HTML tags and attributes in the default-policy.xml file that are allowable on their Blackboard instance, based on their organization's risk tolerance level.

If you’ve customized your default-policy.xml file and Blackboard makes changes to the default version of the file, the previous Blackboard default file is renamed to indicate that it’s an old version. The new default-policy.xml file by Blackboard is added to your policies and is set to be your active policy. You’ll be informed of the file update via email. Your own customized policy is unchanged.

Note

Safe HTML is only applicable to users who don't have the Add/Modify Trusted Content privilege, also called the Add/Edit Trusted Content With Scripts privilege. Users with this privilege can enter unrestricted/trusted HTML, meaning they aren't bound to the Safe HTML rules. By default, Blackboard gives this privilege to Administrators, Course Builders, Graders, Instructors, and Teaching Assistants. All other roles don't have this privilege by default, but it can be added on an as-needed basis.

On the Administrator Panel, select Safe HTML Filters in the Security menu.

Important

Blackboard LMS environments can't be configured to filter custom file types through HTML filters.

Customize a policy

Administrators can customize the list of allowable HTML tags and attributes in the default-policy.xml file based on the needs of their organizations. However, this should be a rare event. Administrators only need to customize the policy if they have a specific use case that the policy doesn't support.

  1. On the Administrator Panel, select Safe HTML Filters in the Security menu.

  2. Select Safe HTML Filter for Content Editor to access the policy list.

  3. Access the menu for the default-policy.xml file and select Download. Save the file on your computer.

  4. Make any changes to the SafeHTML rule to meet the needs of your organization.

  5. When you've edited the file, type a new name.

  6. Return to the Safe HTML Filter for Content Editor page to access the policy list.

  7. Select Upload to access the Upload Safe HTML Policy page and browse for your new file.

  8. Optionally, type a comment.

  9. Select Submit to upload the new file.

  10. The new file appears in the list of policy files. From the file's menu, select Activate to make this the active policy file in your Blackboard environment.

Test a policy

Administrators can test policies to make sure they are functioning properly and yielding the results they want.

  1. On the Administrator Panel, select Safe HTML Filters in the Security menu.

  2. Select Safe HTML Filter for Content Editor.

  3. From the policy file's menu, select Test Policy.

  4. In the Enter code (HTML, JS) to Test field, enter any HTML code that you want to test.

  5. Select Test.

The system provides test results, based on the HTML code entered, such as these:

  • A new Sanitized Output field appears showing you the system-sanitized output for the HTML you entered.

  • If the script tag you entered isn't allowed by the policy, a message appears telling you the script isn't allowed for security reasons.

  • A tag may contain an attribute that can't be processed. In this case, a message appears with the tag that contains an attribute that can't be processed and has been filtered out.

HTML body tags and attributes

The default-policy.xml file allows these body tags and attributes.

Grouping elements

Tag

Attributes

div

id, class, lang, dir, title, style, align

span

id, class, dir, title, style, align, xml:lang

Headings

Tag

Attributes

h1

id, class, lang, dir, title, style, align

h2

id, class, lang, dir, title, style, align

h3

id, class, lang, dir, title, style, align

h4

id, class, lang, dir, title, style, align

h5

id, class, lang, dir, title, style, align

h6

id, class, lang, dir, title, style, align

Address

Tag

Attributes

address

id, class, lang, dir, title, style

Font Style and HR Tags and Attributes

The default-policy.xml file ships with these font style and HR tags and attributes.

Font style

Tag

Attributes

tt

id, class, lang, dir, title, style

i

id, class, lang, dir, title, style

b

id, class, lang, dir, title, style

big

id, class, lang, dir, title, style

small

id, class, lang, dir, title, style

HR

Tag

Attribute

hr

id, class, lang, dir, title, style

List tags and attributes

The default-policy.xml file ships with these list tags and attributes.

Unordered lists, ordered lists, and list items

Tag

Attributes

ul

id, class, lang, dir, title, style

li

id, class, lang, dir, title, style

ol

id, class, lang, dir, title, style

Definition lists

Tag

Attributes

dl

id, class, lang, dir, title, style

dt

id, class, lang, dir, title, style

dd

id, class, lang, dir, title, style

dir

id, class, dir, title, style, compact

menu

id, class, lang, dir, title, style, compact

The default-policy.xml file ships with these link tags and attributes.

Links

Tag

Attributes

a

class, dir, id, lang, name, rel, rev, style, target = _blank, title, xml:lang, accesskey, tabindex, charset, coords, href, hreflang, name, shape

link

See http://www.w3schools.com/tags/tag_link.asp.

Text tags and attributes

The default-policy.xml file ships with these text tags and attributes.

Phrase elements

Tag

Attributes

em

id, class, lang, dir, title, style

strong

id, class, lang, dir, title, style

cite

id, class, lang, dir, title, style

dfn

id, class, lang, dir, title, style

code

id, class, lang, dir, title, style

samp

id, class, lang, dir, title, style

kbd

id, class, lang, dir, title, style

var

id, class, lang, dir, title, style

abbr

id, class, lang, dir, title, style

acronym

id, class, lang, dir, title, style

Quotations

Tag

Attributes

blockquote

id, class, lang, dir, title, style

q

id, class, lang, dir, title, style

Subscripts and superscripts

Tag

Attributes

sub

id, class, lang, dir, title, style

sup

id, class, lang, dir, title, style

Lines and paragraphs

Tag

Attributes

p

id, class, lang, dir, title, stye, align

br

id, class, title, style, clear

pre

id, class, lang, dir, title, style

Marking document changes

Tag

Attributes

ins

id, class, lang, dir, title, style

del

id, class, lang, dir, title, style

Table tags and attributes

The default-policy.xml file ships with these table tags and attributes.

Table

Tag

Attributes

table

id, border, cellpadding, cellspacing, align, class, frame, summary, lang, dir, style, bgcolor, width, rules, dir

Table captions

Tag

Attributes

caption

id, lang, dir, title, style

Row groups

Tag

Attributes

thead

cellhalign, cellvalign, id, class, lang, dir, title, style, align, char, charoff, valign

tfoot

cellhalign, cellvalign, id, class, lang, dir, title, style, align, char, charoff, valign

tbody

id, class, lang, dir, title, style, align, char, charoff, valign

pre

id, class, lang, dir, title, style

Column groups

Tag

Attributes

colgroup

span, width, id, class, lang, dir, title, style, align, char, charoff, valign

col

span, width, id, class, lang, dir, title, style, align, char, charoff, valign

Table rows

Tag

Attributes

tr

id, class, lang, dir, title, style, bgcolor, align, char, charoff, valign

Table cells

Tag

Attributes

th

abbr, axis, headers, scope, rowspan, colspan, id, class, lang, dir, title, style, bgcolor, align, char, charoff, valign

td

abbr, axis, headers, scope, rowspan, colspan, id, class, lang, dir, title, style, bgcolor, align, char, charoff, valign

Embedded media and Mashup tags and attributes

The default-policy.xml file ships with these embedded media and mashup tags and attributes.

Partners

Tag

Attributes

script

type, charset, src

iframe

src=starts with SafeHTML Restricted Youtube Sources or building blocks, longdesc, name, width, height, id, class, title, style, align, frameborder, marginwidth, marginheight, scrolling

Images

Tag

Attributes

img

src, alt, longdesc, name, id, class, lang, dir, title, style, align, width, height, border, hspace, vspace

YouTube

Tag

Attributes

object

classid, codebase, codetype, data, type, archive, declare, standby, id, class, lang, dir, title, style, tabindex, name, align, width, height, border, hspace, vspace

param

name=movie, value=starts with SafeHTML Restricted Youtube Sources, name = allowscriptaccess, value=true, name=allowfullscreen, value=true|false

embed

src=starts with SafeHTML Restricted Youtube Sources, allowScriptAccess=never, allowNetworking=internal, type=application/x-shockwave-flash, id, width, height, type, quality, scale, salign, wmode, base, name, align, hspace, vspace, bgcolor, sound, progress, swstretchstyle, swstretchalign, swstretchvalign

iframe

src=starts with http(s)://www.youtube.com or http(s)://www.youtube-nocookie.com/, longdesc, name, width, height, id, class, title, style, align, frameborder, marginwidth, marginheight, scrolling

Slideshare

Tag

Attributes

object

classid, codebase, codetype, data, type, archive, declare, standby, id, class, lang, dir, title, style, tabindex, name, align, width, height, border, hspace, vspace

param

name=movie, value=starts with http(s)://static.slidesharecdn.com/ or http(s)://www.slideshare.net/, name=allowscriptaccess, value=never, name=allowfullscreen, value=true|false, name=wmode, value=transparent

embed

src=starts with http(s)://static.slidesharecdn.com/ or http(s)://www.slideshare.net/, allowScriptAccess=never, allowNetworking=never, wmode=transparent, type=application/x-shockwave-flash, id, width, height, type, quality, scale, salign, base, name, align, hspace, vspace, bgcolor, sound, progress, autostart=false, swstretchstyle, swstretchalign, swstretchvalign

iframe

src=starts with http(s)://static.slidesharecdn.com/ or http(s)://www.slideshare.net/, height, width, frameborder, marginwidth, marginheight, scrolling

Other media types including Flash

Tag

Attributes

Comments

object

codebase, name, align, hspace, vspace, bgcolor, classid

param

name=allowScriptAccess, value=never, name=allowNetworking, value=none, name=autostart, value=false

May contain other parameters, but these must always be present for sources other than youtube and slideshare.

embed

allowScriptAccess=never, allowNetworking=none, autostart=false, allowFullScreen=false, type=... see comment, wmode=window/transparent/opaque, id, class, dir, flashvars, height, lang, name, src, style, title, width, xml:lang

allowScriptAccess=never must always be present for Flash

allowNetworking=none must always be present for Flash

allowFullScreen=false must always be present for Flash

"type" is not restricted currently to our supported media types, but the default policy will eventually be limited to:

  • video/quicktime

  • application/x-shockwave-flash

  • application/x-director

  • application/x-mplayer2

iframe

src=restricted list, longdesc, name, width, height, id, class, title, style, align, frameborder, marginwidth, marginheight, scrolling