Chrome Version 63.0.3239.132 (Windows 10, latest creators update)
uMatrix Version 1.2.0

I have an internal webpage for my company that uses many iframes to display content (even iframes within iframes). After allowing chrome to install the latest version, this website no longer works properly. When using the developer console, I can see the page requests for the iframe data is mangled. A small snippet of some of the data:

�‹��í½�`�I–%&/mÊ{�JõJ×àt¡�€`�$Ø�@�ìÁˆÍæ’ì�iG#)«*�ÊeVe]f�@Ìí�¼÷Þ{ï½÷Þ{ï½÷º;�N'÷ßÿ?\fd�löÎJÚÉž!€ªÈ�?~|�?"�ÿ®O¿šÎëj‘�¶û‘ôÃ�–�}òÑe‘_­ªºõ^º*fíü³Y~YLómþc”�Ë¢-²r»™f%Á�ï($�Ó÷Šóôì4=ø>�òc�›i]¬Ú´½^�ø6�×Þýéì2“Oå­�»*–³êj\VS¸ZŽçu~ž~–~Ô.Ú:›¾�ÏÊò÷hæyY~Fôú…M;{™]ä¿°Í�«2kóÏòº^/›õ xç³_¸È›†¾ÿlï£C†þø®tÆ}=þ]¿—/gÅù÷ �å»�ôÒ¦ž~ö‘ûàîÞ½Ýݽ�ÝOïß»�÷^=[eu{}·¬.ö]›ñO7��y}r/La�ŽN„ºÛo¨_�ÖŒ±@y˜NçYÝäíg_½y¶}ðQz—@õÁ¼ÇT��Aëë—FyAüÙ�Ýf�Ôä|½œbZÓf²x^]¼nד­;¿ø—üƉû{¼ª«¶��šö_ü�'iŠ‰Ï�¥æ]¼0Âç³|

Under normal circumstances this would be HTML. I narrowed down the issue to uMatrix by disabling a single plugin at a time. With uMatrix enabled, I see the problem consistently on with my internal website (note: I do have other sites that use far fewer iframes that do not show the problem). With uMatrix disabled, I see the problem with one or more iframes for this particular site. I do not believe it is necessarily related what rules are enabled as my first attempt at resolving the problem was simply to disable uMatrix for the base level domain. That seems to have had no impact on the issue.

I believe it is directly related to iframe processing as I can capture the URL that would be displayed in the iframe, load it as an individual tab, and the data loads completely normally, even with uMatrix enabled for the domain.

Something about this issues seems to be transient as well. As noted above, it doesn't happen to all pages with iframes, only on a particular page that has many iframes. If I refresh the page multiple times, some of the iframes will sometimes load correctly. More curiously, which iframes load correctly seems to change from refresh to refresh.