Contact has 161 MB because of (automated) social media avatar

Describe the bug

I noticed out of memory errors on my phone related to DavX5 synchronization (Nextcloud <-> Android). After digging around for a few hours, I saw that one of my Nextcloud contacts has 161MB because of an avatar that was downloaded automatically. The VCF file shows

PHOTO;ENCODING=B;TYPE=PNG;VALUE=BINARY:iVBORw0KGgoAAAANSUhEUgAAAtAAAALQCAYA
 AAC5V0ecAAAACXBIWXMAAA7EAAAOxAGVKw4bAAAgAElEQVR42sy92ZIkObIldhSAmW+RGblU1n

and then endless lines of photo data.

Has this been an issue for other users? Did you already encounter such a problem?

Thanks for looking into this!

Steps to reproduce

I didn't do anything special. Just added the contact a while ago. (Email, and name).

Expected behavior

Avatars are small.

Actual behavior

Avatar has 161MB.

Contact version

No response

Operating system

No response

PHP engine version

No response

Web server

No response

Database

No response

Operating system

No response

List of activated Apps

Contacts.

Nextcloud Signing status

No response

Configuration report

No response

Additional info

No response

Start with the Contacts app's generated VCF data, especially the PHOTO;ENCODING=B;TYPE=PNG;VALUE=BINARY field, and reproduce synchronization with the affected Android client if possible. Trace how the avatar is obtained and written to the contact, then verify that synchronization no longer produces an unexpectedly large avatar or out-of-memory failure.