Update SVG sanitizer to conform to SVG 1.1

Use a custom Loofah scrubber since sanitize 2.x transformers are inadequate
to handle case-sensitive SVG attributes. sanitize parses documents as HTML
instead of XML, which causes all SVG attribute names (e.g. viewBox) to be downcased.

* SVG element list: https://www.w3.org/TR/SVG/eltindex.html
* SVG attribute list: https://www.w3.org/TR/SVG/attindex.html

Closes #14555

2 files changed, 100 insertions, 0 deletions

diff --git a/spec/fixtures/sanitized.svg b/spec/fixtures/sanitized.svg
new file mode 100644
index 00000000000..8f84b8f5e20
--- /dev/null
+++ b/spec/fixtures/sanitized.svg
@@ -0,0 +1,50 @@
+<?xml version="1.0"?>
+<svg xmlns="http://www.w3.org/2000/svg" id="Layer_1" data-name="Layer 1" viewBox="0 0 622 682">
+  
+  <defs>
+    <style>.cls-1{fill:#30353e;}.cls-2{fill:#8c929d;}.cls-3{fill:#fc6d26;}.cls-4{fill:#e24329;}.cls-5{fill:#fca326;}</style>
+  </defs>
+  <title>stacked_wm</title>
+  <path id="bg" class="cls-1" d="M622,681H0V-1H622V681h0Z"/>
+  <g id="g12">
+    <path id="path14" class="cls-2" d="M316.89,497.72h-19l0.06,141.74H375V621.93h-58l-0.06-124.22h0Z"/>
+  </g>
+  <g id="g24">
+    <path id="path26" class="cls-2" d="M448.32,614.57a32.46,32.46,0,0,1-23.59,10c-14.5,0-20.35-7.14-20.35-16.45,0-14.07,9.74-20.77,30.52-20.77a86.46,86.46,0,0,1,13.42,1.08v26.19h0Zm-19.7-85.91a63.45,63.45,0,0,0-40.5,14.53l6.73,11.66c7.79-4.54,17.32-9.09,31-9.09,15.58,0,22.51,8,22.51,21.42v6.93a81.48,81.48,0,0,0-13.2-1.08c-33.33,0-50.22,11.69-50.22,36.14,0,21.86,13.42,32.89,33.76,32.89,13.71,0,26.84-6.28,31.38-16.45l3.46,13.85h13.42V567c0-22.94-10-38.3-38.31-38.3h0Z"/>
+  </g>
+  <g id="g28">
+    <path id="path30" class="cls-2" d="M528.4,625.18c-7.14,0-13.42-.87-18.18-3V556.58c6.49-5.41,14.5-9.31,24.68-9.31,18.4,0,25.54,13,25.54,34,0,29.86-11.47,43.93-32,43.93m8-96.52a34.88,34.88,0,0,0-26.19,11.58V522l-0.06-24.24H491.54L491.6,636c9.31,3.9,22.08,6.06,35.93,6.06,35.5,0,52.6-22.72,52.6-61.89,0-30.95-15.8-51.51-43.73-51.51"/>
+  </g>
+  <g id="g32">
+    <path id="path34" class="cls-2" d="M109.84,513.08c16.88,0,27.7,5.63,34.85,11.25l8.19-14.18c-11.16-9.78-26.16-15-42.17-15-40.47,0-68.83,24.67-68.83,74.44,0,52.15,30.59,72.5,65.58,72.5a111,111,0,0,0,42.21-8.22l-0.4-55.72V560.58H97.32v17.53h33.12l0.4,42.31c-4.33,2.16-11.9,3.9-22.08,3.9-28.14,0-47-17.7-47-55,0-37.87,19.48-56.26,48.05-56.26"/>
+  </g>
+  <g id="g36">
+    <path id="path38" class="cls-2" d="M243.79,497.72H225.17l0.06,23.8v82.23c0,22.94,10,38.3,38.31,38.3A64.16,64.16,0,0,0,275,641V624.31a57,57,0,0,1-8.66.65c-15.58,0-22.51-8-22.51-21.42v-56.7H275V531.26H243.85l-0.06-33.54h0Z"/>
+  </g>
+  <path id="path40" class="cls-2" d="M177.94,639.46h18.61V531.26H177.94v108.2h0Z"/>
+  <path id="path42" class="cls-2" d="M177.94,516.33h18.61V497.72H177.94v18.61h0Z"/>
+  <g id="g44">
+    <path id="path46" class="cls-3" d="M525.05,266.23l-24-74L453.36,45.6a8.19,8.19,0,0,0-15.58,0L390.12,192.24H231.88L184.22,45.6a8.19,8.19,0,0,0-15.58,0L121,192.24l-24,74a16.38,16.38,0,0,0,6,18.31L311,435.71,519.1,284.54a16.38,16.38,0,0,0,6-18.31"/>
+  </g>
+  <g id="g48">
+    <path id="path50" class="cls-4" d="M311,435.71h0l79.12-243.47H231.88L311,435.71h0Z"/>
+  </g>
+  <g id="g56">
+    <path id="path58" class="cls-3" d="M311,435.71L231.88,192.24H121L311,435.71h0Z"/>
+  </g>
+  <g id="g64">
+    <path id="path66" class="cls-5" d="M121,192.24h0l-24,74a16.37,16.37,0,0,0,6,18.31L311,435.7,121,192.24h0Z"/>
+  </g>
+  <g id="g72">
+    <path id="path74" class="cls-4" d="M121,192.24H231.88L184.22,45.6a8.19,8.19,0,0,0-15.58,0L121,192.24h0Z"/>
+  </g>
+  <g id="g76">
+    <path id="path78" class="cls-3" d="M311,435.71l79.12-243.47H501L311,435.71h0Z"/>
+  </g>
+  <g id="g80">
+    <path id="path82" class="cls-5" d="M501,192.24h0l24,74a16.37,16.37,0,0,1-6,18.31L311,435.7,501,192.24h0Z"/>
+  </g>
+  <g id="g84">
+    <path id="path86" class="cls-4" d="M501,192.24H390.12L437.78,45.6a8.19,8.19,0,0,1,15.58,0L501,192.24h0Z"/>
+  </g>
+</svg>
diff --git a/spec/fixtures/unsanitized.svg b/spec/fixtures/unsanitized.svg
new file mode 100644
index 00000000000..3957557334b
--- /dev/null
+++ b/spec/fixtures/unsanitized.svg
@@ -0,0 +1,50 @@
+<?xml version="1.0"?>
+<svg xmlns="http://www.w3.org/2000/svg" id="Layer_1" data-name="Layer 1" viewBox="0 0 622 682" filterMe="test">
+  <iframe src="http://www.google.com"></iframe>
+  <defs>
+    <style>.cls-1{fill:#30353e;}.cls-2{fill:#8c929d;}.cls-3{fill:#fc6d26;}.cls-4{fill:#e24329;}.cls-5{fill:#fca326;}</style>
+  </defs>
+  <title>stacked_wm</title>
+  <path id="bg" class="cls-1" d="M622,681H0V-1H622V681h0Z"/>
+  <g id="g12">
+    <path id="path14" class="cls-2" d="M316.89,497.72h-19l0.06,141.74H375V621.93h-58l-0.06-124.22h0Z"/>
+  </g>
+  <g id="g24">
+    <path id="path26" class="cls-2" d="M448.32,614.57a32.46,32.46,0,0,1-23.59,10c-14.5,0-20.35-7.14-20.35-16.45,0-14.07,9.74-20.77,30.52-20.77a86.46,86.46,0,0,1,13.42,1.08v26.19h0Zm-19.7-85.91a63.45,63.45,0,0,0-40.5,14.53l6.73,11.66c7.79-4.54,17.32-9.09,31-9.09,15.58,0,22.51,8,22.51,21.42v6.93a81.48,81.48,0,0,0-13.2-1.08c-33.33,0-50.22,11.69-50.22,36.14,0,21.86,13.42,32.89,33.76,32.89,13.71,0,26.84-6.28,31.38-16.45l3.46,13.85h13.42V567c0-22.94-10-38.3-38.31-38.3h0Z"/>
+  </g>
+  <g id="g28">
+    <path id="path30" class="cls-2" d="M528.4,625.18c-7.14,0-13.42-.87-18.18-3V556.58c6.49-5.41,14.5-9.31,24.68-9.31,18.4,0,25.54,13,25.54,34,0,29.86-11.47,43.93-32,43.93m8-96.52a34.88,34.88,0,0,0-26.19,11.58V522l-0.06-24.24H491.54L491.6,636c9.31,3.9,22.08,6.06,35.93,6.06,35.5,0,52.6-22.72,52.6-61.89,0-30.95-15.8-51.51-43.73-51.51"/>
+  </g>
+  <g id="g32">
+    <path id="path34" class="cls-2" d="M109.84,513.08c16.88,0,27.7,5.63,34.85,11.25l8.19-14.18c-11.16-9.78-26.16-15-42.17-15-40.47,0-68.83,24.67-68.83,74.44,0,52.15,30.59,72.5,65.58,72.5a111,111,0,0,0,42.21-8.22l-0.4-55.72V560.58H97.32v17.53h33.12l0.4,42.31c-4.33,2.16-11.9,3.9-22.08,3.9-28.14,0-47-17.7-47-55,0-37.87,19.48-56.26,48.05-56.26"/>
+  </g>
+  <g id="g36">
+    <path id="path38" class="cls-2" d="M243.79,497.72H225.17l0.06,23.8v82.23c0,22.94,10,38.3,38.31,38.3A64.16,64.16,0,0,0,275,641V624.31a57,57,0,0,1-8.66.65c-15.58,0-22.51-8-22.51-21.42v-56.7H275V531.26H243.85l-0.06-33.54h0Z"/>
+  </g>
+  <path id="path40" class="cls-2" d="M177.94,639.46h18.61V531.26H177.94v108.2h0Z"/>
+  <path id="path42" class="cls-2" d="M177.94,516.33h18.61V497.72H177.94v18.61h0Z"/>
+  <g id="g44">
+    <path id="path46" class="cls-3" d="M525.05,266.23l-24-74L453.36,45.6a8.19,8.19,0,0,0-15.58,0L390.12,192.24H231.88L184.22,45.6a8.19,8.19,0,0,0-15.58,0L121,192.24l-24,74a16.38,16.38,0,0,0,6,18.31L311,435.71,519.1,284.54a16.38,16.38,0,0,0,6-18.31"/>
+  </g>
+  <g id="g48">
+    <path id="path50" class="cls-4" d="M311,435.71h0l79.12-243.47H231.88L311,435.71h0Z"/>
+  </g>
+  <g id="g56">
+    <path id="path58" class="cls-3" d="M311,435.71L231.88,192.24H121L311,435.71h0Z"/>
+  </g>
+  <g id="g64">
+    <path id="path66" class="cls-5" d="M121,192.24h0l-24,74a16.37,16.37,0,0,0,6,18.31L311,435.7,121,192.24h0Z"/>
+  </g>
+  <g id="g72">
+    <path id="path74" class="cls-4" d="M121,192.24H231.88L184.22,45.6a8.19,8.19,0,0,0-15.58,0L121,192.24h0Z"/>
+  </g>
+  <g id="g76">
+    <path id="path78" class="cls-3" d="M311,435.71l79.12-243.47H501L311,435.71h0Z"/>
+  </g>
+  <g id="g80">
+    <path id="path82" class="cls-5" d="M501,192.24h0l24,74a16.37,16.37,0,0,1-6,18.31L311,435.7,501,192.24h0Z"/>
+  </g>
+  <g id="g84">
+    <path id="path86" class="cls-4" d="M501,192.24H390.12L437.78,45.6a8.19,8.19,0,0,1,15.58,0L501,192.24h0Z"/>
+  </g>
+</svg>