Fix various legacy problems (#37092)

1.  Fix #36439
2. Fix #37089
3. Fix incorrect layout of admin auth oidc page
4. Fix #35866
5. Fix #35800
6. Fix #36243

modules/markup/sanitizer_default_test.go

@@ -58,6 +58,9 @@ func TestSanitizer(t *testing.T) {
 		`<a href="cbthunderlink://somebase64string)">my custom URL scheme</a>`, `<a href="cbthunderlink://somebase64string)" rel="nofollow">my custom URL scheme</a>`,
 		`<a href="matrix:roomid/psumPMeAfzgAeQpXMG:feneas.org?action=join">my custom URL scheme</a>`, `<a href="matrix:roomid/psumPMeAfzgAeQpXMG:feneas.org?action=join" rel="nofollow">my custom URL scheme</a>`,
 
+		// picture
+		`<picture><source media="a"><source media="b"><img alt="c" src="d"></picture>`, `<picture><source media="a"><source media="b"><img alt="c" src="d"></picture>`,
+
 		// Disallow dangerous url schemes
 		`<a href="javascript:alert('xss')">bad</a>`, `bad`,
 		`<a href="vbscript:no">bad</a>`, `bad`,