290396 2025-03-25 10:05:46 -0700 Form controls inside a declarative shadow DOM erroneously get associated with form element in an outer tree 2025-03-26 08:21:15 -0700 1 1 1 Unclassified WebKit Forms Safari 18 Unspecified Unspecified RESOLVED FIXED HTML5, InRadar P2 Normal --- 148695 1 konnor5456 rniwa cdumez nathan rniwa webkit-bug-importer wenson_hsieh oldest_to_newest 2105904 0 konnor5456 2025-03-25 10:05:46 -0700 ## Explanation In Desktop Safari 17.5 and 18.3.1 and iOS Safari 18.3.2 (only tested versions so far) a form control rendered inside a declarative shadow DOM leak into the host element's form. This does not happen in Firefox 136 or Chrome 134. Essentially when you have the following: <form> <x-element> <template shadowrootmode="open"> <input name="foo" value="bar"> </template> </x-element> </form> the FormData you will get the following: formData.getAll("foo") // => ["bar"] only in Safari. In Firefox and Chrome you will get an empty array. In addition, doing `form.elements` returns form controls from the shadow dom in Safari. This does not happen when the shadow dom is client side rendered *only* when its rendered via Declarative Shadow DOM. This feels like unintended and unexpected behavior. https://codepen.io/paramagicdev/pen/gbOjxJy ^ reproduction 2106050 1 474714 rniwa 2025-03-25 18:50:50 -0700 Created attachment 474714 Reduction 2106051 2 474715 rniwa 2025-03-25 19:15:39 -0700 Created attachment 474715 More test cases 2106083 3 rniwa 2025-03-25 23:55:58 -0700 Pull request: https://github.com/WebKit/WebKit/pull/43034 2106086 4 konnor5456 2025-03-26 00:32:26 -0700 As an additional note, the same mechanism seems to affect button submissions as well: https://codepen.io/paramagicdev/pen/bNGjmZg buttons clicked inside a declarative shadow dom cause a form in an outer tree to submit. 2106138 5 ews-feeder 2025-03-26 08:20:15 -0700 Committed 292703@main (e657338dfd41): <https://commits.webkit.org/292703@main> Reviewed commits have been landed. Closing PR #43034 and removing active labels. 2106139 6 webkit-bug-importer 2025-03-26 08:21:15 -0700 <rdar://problem/147932589> 474714 2025-03-25 18:50:50 -0700 2025-03-25 18:50:50 -0700 Reduction bug290396.html text/html 224 rniwa PCFET0NUWVBFIGh0bWw+Cjxmb3JtPgo8c29tZS1lbGVtZW50Pgo8dGVtcGxhdGUgc2hhZG93cm9v dG1vZGU9ImNsb3NlZCI+CjxpbnB1dCBuYW1lPSJlbWFpbCIgdmFsdWU9ImJsYWgiPgo8L3RlbXBs YXRlPgo8L3NvbWUtZWxlbWVudD4KPC9mb3JtPgo8c2NyaXB0Pgpkb2N1bWVudC53cml0ZShkb2N1 bWVudC5mb3Jtc1swXVsnZW1haWwnXSA/ICdGQUlMJyA6ICdQQVNTJyk7Cjwvc2NyaXB0Pgo= 474715 2025-03-25 19:15:39 -0700 2025-03-25 19:15:39 -0700 More test cases bug290396.html text/html 758 rniwa PCFET0NUWVBFIGh0bWw+Cjxmb3JtPgo8c29tZS1lbGVtZW50Pjx0ZW1wbGF0ZSBzaGFkb3dyb290 bW9kZT0ib3BlbiI+PGlucHV0IG5hbWU9ImVtYWlsIj48Zm9ybT48aW5wdXQgbmFtZT0ibmlja25h bWUiPjwvZm9ybT48L3RlbXBsYXRlPjwvc29tZS1lbGVtZW50Pgo8aW5wdXQgbmFtZT0ibmFtZSI+ CjwvZm9ybT4KPHNjcmlwdD4KZG9jdW1lbnQud3JpdGUoZG9jdW1lbnQuZm9ybXNbMF1bJ2VtYWls J10gPyAnRkFJTCcgOiAnUEFTUycpOwpkb2N1bWVudC53cml0ZSgnPGJyPicpOwpkb2N1bWVudC53 cml0ZShkb2N1bWVudC5mb3Jtc1swXVsnbmlja25hbWUnXSA/ICdGQUlMJyA6ICdQQVNTJyk7CmRv Y3VtZW50LndyaXRlKCc8YnI+Jyk7CmRvY3VtZW50LndyaXRlKGRvY3VtZW50LmZvcm1zWzBdWydu YW1lJ10gPyAnUEFTUycgOiAnRkFJTCcpOwpkb2N1bWVudC53cml0ZSgnPGJyPicpOwpkb2N1bWVu dC53cml0ZShkb2N1bWVudC5xdWVyeVNlbGVjdG9yKCdzb21lLWVsZW1lbnQnKS5zaGFkb3dSb290 LmlubmVySFRNTCA9PSAnPGlucHV0IG5hbWU9ImVtYWlsIj48Zm9ybT48aW5wdXQgbmFtZT0ibmlj a25hbWUiPjwvZm9ybT4nID8gJ1BBU1MnIDogJ0ZBSUwnKTsKZG9jdW1lbnQud3JpdGUoJzxicj4n KTsKZG9jdW1lbnQud3JpdGUoZG9jdW1lbnQucXVlcnlTZWxlY3Rvcignc29tZS1lbGVtZW50Jyku c2hhZG93Um9vdC5xdWVyeVNlbGVjdG9yKCdmb3JtJylbJ25pY2tuYW1lJ10gPyAnUEFTUycgOiAn RkFJTCcpCjwvc2NyaXB0Pgo=