Remove hidden formatting when user paste text from MS Word into TinyMCE

Around a fifth of post submissions that I receive contains ridiculous amounts of hidden formatting.

For example, here is some of it from a recent post:

!--[if gte mso 9]xml
w:WordDocument
w:ViewNormal/w:View
w:Zoom0/w:Zoom
w:TrackMoves/
w:TrackFormatting/
w:PunctuationKerning/
w:ValidateAgainstSchemas/
w:SaveIfXMLInvalidfalse/w:SaveIfXMLInvalid
w:IgnoreMixedContentfalse/w:IgnoreMixedContent
w:AlwaysShowPlaceholderTextfalse/w:AlwaysShowPlaceholderText
w:DoNotPromoteQF/
w:LidThemeOtherEN-US/w:LidThemeOther
w:LidThemeAsianX-NONE/w:LidThemeAsian
w:LidThemeComplexScriptX-NONE/w:LidThemeComplexScript
w:Compatibility
w:BreakWrappedTables/
w:SnapToGridInCell/
w:WrapTextWithPunct/
w:UseAsianBreakRules/
w:DontGrowAutofit/
w:SplitPgBreakAndParaMark/
w:EnableOpenTypeKerning/
w:DontFlipMirrorIndents/
w:OverrideTableStyleHps/
/w:Compatibility
m:mathPr
m:mathFont m:val="Cambria Math"/
m:brkBin m:val="before"/
m:brkBinSub m:val="#45;-"/
m:smallFrac m:val="off"/
m:dispDef/
m:lMargin m:val="0"/
m:rMargin m:val="0"/
m:defJc m:val="centerGroup"/
m:wrapIndent m:val="1440"/
m:intLim m:val="subSup"/
m:naryLim m:val="undOvr"/
/m:mathPr/w:WordDocument
/xml![endif]--!--[if gte mso 9]xml
w:LatentStyles DefLockedState="false" DefUnhideWhenUsed="true"
DefSemiHidden="true" DefQFormat="false" DefPriority="99"
LatentStyleCount="267"
w:LsdException Locked="false" Priority="0" SemiHidden="false"
UnhideWhenUsed="false" QFormat="true" Name="Normal"/
w:LsdException Locked="false" Priority="9" SemiHidden="false"
UnhideWhenUsed="false" QFormat="true" Name="heading 1"/
w:LsdException Locked="false" Priority="9" QFormat="true" Name="heading 2"/
w:LsdException Locked="false" Priority="9" QFormat="true" Name="heading 3"/
w:LsdException Locked="false" Priority="9" QFormat="true" Name="heading 4"/
w:LsdException Locked="false" Priority="9" QFormat="true" Name="heading 5"/
w:LsdException Locked="false" Priority="9" QFormat="true" Name="heading 6"/
w:LsdException Locked="false" Priority="9" QFormat="true" Name="heading 7"/
w:LsdException Locked="false" Priority="9" QFormat="true" Name="heading 8"/
w:LsdException Locked="false" Priority="9" QFormat="true" Name="heading 9"/
w:LsdException Locked="false" Priority="39" Name="toc 1"/
w:LsdException Locked="false" Priority="39" Name="toc 2"/
w:LsdException Locked="false" Priority="39" Name="toc 3"/
w:LsdException Locked="false" Priority="39" Name="toc 4"/

It is actually 650 lines, view it all here.

Also, random HTML formatting is added to tags like:

p class="MsoNormal"

Upon further interesting research, it appears that this happens when the author paste content from MS Word directly into the TinyMCE visual editor. And as detailed:

The bad news isn’t evident until someone attempts to view that page with a different browser and the page is totally misformatted or appears blank. Ironically, this latter scenario happens most often when the page is viewed in Microsoft Internet Explorer [Good!].

A way to solve it may be to use the Paste from Word button.

However, that is not a viable solution when 20% of submissions have this issue. Is there any way to strip this nonsense formatting upon paste?